I know that linkshells are unique in their having a kind of "in lore" thing compared to chat channels in other games but I'm wondering if it's some consideration for memory management to consoles or what not as it might be with the FC as well, 8 times X number of members could lead to significant resource use, but I'm not exactly sure how much of that would be server side and whatnot.

They're higher than in FFXI but I don't think we're going to find out what the developer reasoning is this time around, but maybe it could be raised in time? We tend to forget that we're basically in the first iteration of a new game with no expansions yet, there is loads to be done and to come.