Even if the entire task group has been destroyed, LVTs and PTs can continue to be launched there until the CV respawns somewhere else. Once that happens, the base that was taken is vulnerable to a take-back and usually there is a horde determined to do so vs. some GV defenders grimly hanging on with minimal air cover. A lot of fun for both sides!
This has happened once and MAYBE twice in all my years of playing this game where a significant force stopped the resupply, took a town and was able to bring troops OR being successful in defending against. More often than not, there is the attitude of why do we have to defend when I see 2 guys already there or attack it if all but almost impossible.
The numbers now a days do not constitute any reason to have this go unfixed. Its a cheap, cheesy and very gamey way of "winning" and needs to go.