That discussion forum was right about the dates.
The original air date for Chef's Chocolate Salty Balls is August 19 1998.
Episode of Saturday Night Live with Schweddy Balls aired on December 12 1998.
The most frequently replayed installment of this sketch, which originally aired on December 12, 1998, featured Alec Baldwin as Christmas treat maker Pete Schweddy, who owned a holiday-themed store called Seasons Eatings. He was famous for his "Schweddy Balls".
The theme of Chef's Chocolate Salty Balls is how Sundance Festival has grown to be a large Hollywood event and how it has commercialized.
From "Where Did The Come From" from South Park Studios Wikia,
The episode is based on how the Sundance Film Festival has grown from a low-budget independent film festival to a large Hollywood event. A couple of years earlier, the Sundance Film Festival rejected Trey and Matt's film Cannibal! The Musical.
So, Chef's salty balls is a reference on how people try to popularize, advertise and sell them in film festivals using their stalls.
Saturday Night Live has a recurring theme Delicious Dish which was introduced in 1996. As a continuation of this theme, Ana Gasteyer wrote a skit named Schweddy Balls to create fun in the Christmas Holiday Season. Source.
Perhaps it is just a coincidence. I have not found supporting evidence that Schweddy Balls is inspired or copied from Chef's Chocolate Salty Balls.