Yes, indeed they might, but if you start seeing sketchy stuff like that, then don't continue, I'm not sure I understand what's hard here. Or do continue, but then if those are AUR packages themselves, review them as such. Personally I just ignore anything not built from official binaries/sources.
If the PKGBUILD depends on more stuff then just officially available things, don't blindly install it and wish for the best. Just like if you "curl | bash" install something, you do at least look at the URL right? It takes a couple of seconds, maybe tens of seconds if you don't recognize the domain/github organization since before.