Nice to hear you having a good time posting your ficlets to AO3! I feel like the "if it is <1000 words it's not worth posting" was something I remember seeing around in my FFnet days in the early 00s, but on AO3 it's more of a "don't like don't read" environment. I think people mostly get annoyed about bad summaries and tags than fic length.

I tended to group my ficlets when I posted on AO3 by fandom or ship more because I am lazy with titles and summaries and tagging, not necessarily because they were "worse" than my longer stuff.