I haven't seen that in the years that I've tried building up meet threads here. Usually there is no meet thread for my cruise at all, and if there is, only a couple of people drop in and say hi once and then don't show up again. I've never seen solicitations.
Disboards is a relatively small pond, which is probably the real reason it's hard to build big groups here for specific cruises. Also, some people on Disboards actively disparage Fish Extender groups, so it might be seen as a less than hospitable environment for them. I've lost count of how many posts I've read here from certain posters who hate FEs. Every time some newbie drops in to ask an FE question, those posters seem to feel the need to comment about how bad the experience is. Why would people try to join an FE group in a forum that seems hostile to FE's?