@trig hey there I am the designer of GW 85. Happy to see a forum here and happy to answer questions and interact as I can.
Task Forces exist in the game because in the 80s the navies organized their naval groups into task forces to do certain things, mainly to protect sealift through enhanced capability to detect surface, air and subsurface threats to the sealift lanes. Capital ships - mainly carriers - were a key cog in this wheel and never moved outside of a task force. So the game recreates that through the task force concept. When a task force conducts combat it can do certain things that a bunch of frigates, subs and destroyers moving alone cannot do.
I wish I could say more but as everything is still being tested, I think it would be best if I didn’t.
Hope this helps!