Before the release of Spider-Man: Far From Home, articles such as this one made the assumption that the film would be part of the Marvel Cinematic Universe's "Phase 4".
Even though Marvel hasn't confirming anything thus far, we actually know quite a bit about what movies are coming up in the MCU's Phase 4.
The only film that is officially confirmed by Marvel Studios is Spider-Man: Far From Home.
Some time later, studio president Kevin Feige said in an interview contradicted this assumption with the unexpected reveal that the film would be a "Phase 3" film instead:
Feige was speaking with Bilibili when he confirmed that Phase 3 of the MCU does not end with Avengers: Endgame, but will instead conclude in Spider-Man: Far From Home.
"It’s the end of the third phase. You’re the first person I’ve told that to," Feige revealed.
What is the significance of Spider-Man: Far From Home being a "Phase 3" film instead of a "Phase 4" film? It seems to me like the movie would have turned out the same regardless of how it was categorized, so I'm not understanding the significance of the move.