Thinking on it now, I wonder if you could put in multiple separate requests to trade out of 2-3 games but all into the same 1 game. I don't think the form would prevent that. They might call or email you to say you can't or simply that there aren't many seats nearby and the additional ones would be further away.
I agree this is probably the case, but I think I would have to call to make sure it all gets set up properly. There are a few times a year (family visits, birthday parties) when I need a bigger block of seats, so I'd have to get them together or else it isn't worth it.