>> If anyone else posted a piece on AO3 related to this event, I didn't notice it. (If anyone knows of any, please point it out!) <<

"Gentleness Is..." (LIFC The Avengers)

>> But because I only managed one independent piece, and have no other pieces to connect it to from other authors, I won't be making an AO3 collection unless September sees that significantly change. <<

You might consider making a broader AO3 collection for Five Moments of Intimacy or Nonsexual Intimacies so you can gather things even if a given event only generates a few new fanfics. That would make it easier for people to find things, and thus encourage more folks to write about nonsexual intimacies.