I think it was both. Sesame Workshop censored it back in season 2, and then Noggin edited it from a season one episode. It doesn't seem like it aired much after season two (and I guess the season one recording was the only copy most fans had all these years).Reminds me of the late 90s-2000s days when we all thought it was just a case of Noggin giving in to political correctness, when we were proven wrong and that this edit happened long before Sesame Unpaved came about.
I remember years ago, reading the lyrics on The Sesame Street Lyrics Archive, and that page actually has the "birdies!" mockery in place of "ya sissy!" This leads me to believe that it was on there, I wonder if the webmaster for that site had a copy or was remembering that line.
I'm hoping that Scott or Shane gets a post-season one episode with "Everyone Likes Ice Cream" soon so we can have confirmation on if it was edited the same way back then. Or somebody can view them at one of the public television archives when they get added. And technically we do not know that it didn't air after season 15 - maybe it is in one of the episodes that the archives has, though there's a lot of unknown episodes to go through (and of course the archives is currently closed).