This is true, but at the same time, it doesn't make sense to put so much effort into this as to prevent you from working on your main project -- the one you want to promote. There's got to be a sweet spot, which may be different for each creator.
And even if two creators are willing to put an equal amount of time/effort into this, they may end up doing two different things with that time. One person may partake in an anthology because they enjoy creating oneshots, while the other person may prefer to make guest comics/ fanarts for existing longform comics.
I would love to see the anthology happen, but I do stress that it's not the only way to go about it. And even within the anthology route, there are multiple options to be explored! (e.g. the illustration option you listed, for people who don't do short stories)
(So I guess I'm not really disagreeing with you per say, just trying to expand on what you're saying?)
Glad it was helpful! Yeah, even though I have future plans for a NSFW short, I don't think a cross promotion of NSFW comics is the right option for me since my main project is largely SFW (and the short is just a side story to that main project). Nevertheless, I'm very interested in seeing where this goes. Community effort done right is an amazing thing.