ResearchGate likes to send notifications when your papers are cited. If you’re signed up for Google Scholar alerts, you’ll already know about most of these, but I confess I usually follow the links anyway. I haven’t previously seen too many preprints reported on ResearchGate, but I don’t see any reason researchers shouldn’t do so. One thing I noticed, though, is that that there’s no link to the preprint!
That “Request file” button opens a pre-populated email to the author, and as I’ve previously mentioned, this is often a good (and legal) way to obtain a paywalled paper you don’t have access to. Preprints on bioRxiv aren’t paywalled, though. There’s no reason ResearchGate couldn’t have included a link to the preprint on the bioRxiv server. They do show the DOI, and you can go to bioRxiv and look it up that way, but why not make the DOI a hyperlink?