There are a few misconceptions in the question.

1. It's unproven that there was a second girl in the bedroom during Ted and Stella's wedding. I don't remember this implication, having watched the show multiple times.
2. Even if there was a third girl, the Bro Code stipulates limitations to "the tricycle". If any of these rules were violated, it would not count as a victory for the belt. As per Article 80:

3. Even if Barney had won the belt during Ted and Stella's wedding, it's not about winning the belt, it's about holding the belt. Whoever holds the belt is considered the reigning champion (like the belt in wrestling, or the yellow shirt in cycling) When Ted allegedly rode the tricycle, he would be taking the belt from Barney, and Barney didn't want the belt to pass on to Ted as he would have to give up his position as reigning champion.

Those are a lot of unproven ifs for your interpretation to be the valid one.

There are a few misconceptions and assumptions in the question.

1. It's unproven that there was a second girl in the bedroom during Ted and Stella's wedding. I don't remember this implication, having watched the show multiple times.
2. Even if there was a third girl, the Bro Code stipulates limitations to "the tricycle". If any of these rules were violated, it would not count as a victory for the belt. As per Article 80:

3. Even if Barney had won the belt during Ted and Stella's wedding, it's not about winning the belt, it's about holding the belt. Whoever holds the belt is considered the reigning champion (like the belt in wrestling, or the yellow shirt in cycling) When Ted allegedly rode the tricycle, he would be taking the belt from Barney, and Barney didn't want the belt to pass on to Ted as he would have to give up his position as reigning champion.

Those are a lot of unproven ifs for your interpretation to be the valid one.

As an aside, Barney's reluctance to let Ted win the belt is in clear violation of Article 80. Barney did admit to his reluctance conflicting with the code during the episode, but there is a clear argument to be made for Barney's title being revoked on grounds of unsportsmanlike conduct. It's even stipulated in the Bro Code itself:

There is no greater affront to the spirit of The Bro Code than a willing violation. [..] any premeditated infraction of The Bro Code is inexcusable. When a Bro violates The Bro Code, he hurts not only his Bros but also himself, because he is no longer Bro worthy.

[..]

If and when a violation occurs, a Bro has the right to administer the offending Bro a level of punishment befitting the infraction. He may choose from the Approved Punishments list.

Approved Punishments

• Revocation of wingman status

• Text blackout
• Designated all-time tip leaver
• Assigned to solar-refraction seat in living room
• Removal from inappropriate email forwards list
• Waterboarding
• Temporary blacklist from barbecues/football Sundays
• Loss of permanent shotgun status
• Bumped from top position on "not using season tickets" list
• Removal from holiday card mailing list
• Revocation of airport picking/drop-off privileges
• Must help offended Bro move heavy furniture
• Temporary removal from usual golf foursome
• Must return stuff loaned from offended Bro…even stuff he thinks his Bro forgot about
• No longer allowed to borrow the truck
• Offended Bro no longer required to bring beer over

There are a few misconceptions in the question.

1. It's unproven that there was a second girl in the bedroom during Ted and Stella's wedding. I don't remember this implication, having watched the show multiple times.
2. Even if there was a third girl, the Bro Code stipulates limitations to "the tricycle". As per Article 80: "The total age of all the three should be less than 83." If that rule was broken, it still wouldn't count as a victory for the belt.
3. I remember a weight limit being mentioned in the show as well, but this is not mentioned in the Bro Code itself. It's unclear whether that's a mistake or an intended change to the rules. It should be considered valid by show standards, which means this is an additional rule that Barney may not have adhered to.
4. Even if Barney had won the belt during Ted and Stella's wedding, it's not about winning the belt, it's about holding the belt. Whoever holds the belt is considered the reigning champion (like the belt in wrestling, or the yellow shirt in cycling) When Ted allegedly rode the tricycle, he would be taking the belt from Barney, and Barney didn't want the belt to pass on to Ted as he would have to give up his position as reigning champion.

Those are a lot of unproven ifs for your interpretation to be the valid one.

There are a few misconceptions in the question.

1. It's unproven that there was a second girl in the bedroom during Ted and Stella's wedding. I don't remember this implication, having watched the show multiple times.
2. Even if there was a third girl, the Bro Code stipulates limitations to "the tricycle". If any of these rules were violated, it would not count as a victory for the belt. As per Article 80:

3. Even if Barney had won the belt during Ted and Stella's wedding, it's not about winning the belt, it's about holding the belt. Whoever holds the belt is considered the reigning champion (like the belt in wrestling, or the yellow shirt in cycling) When Ted allegedly rode the tricycle, he would be taking the belt from Barney, and Barney didn't want the belt to pass on to Ted as he would have to give up his position as reigning champion.

Those are a lot of unproven ifs for your interpretation to be the valid one.