A follower board, in my opinion, is not a 'necessary' part of a tbh. it can come in quite handy and much as any tool, depends on how it is used.
Some of my tbh's have follower boards, some don't.
Those that don't the bees set up shop where they will ( still usually closest to the entrance) if there is too much space on both sides, I will move them bars as close to the entrance as I can, leaving them plenty of room to expand to the back