Even a couple of weeks only needs a wipe with a sponge and no permanent growth. 4 weeks is definitely too much time, as the cleanup is much more challenging.
I did apply anti-fouling to the immersed glass parts of my dinghy but not to the hypalon parts. So far, that paint has lasted 3 summers and when I redo it it will be due to grinding it off on beaching not because the anti-fouling properties have stopped working. So far, I haven't seen any need to apply it to the hypalon parts.