Hickory is much stronger in tension than compression, so heat treating evens things out a bit and helps to reduce set. It's very similar to trapping the back in this effect. They both help to even this inequality. One by hardening the belly and also ups the poundage a bit, the other reduces thr amount of material contributing to the amount of tension and also drops a couple pounds of draw. Both will make for a lighter weight for poundage bow and both reduce the amount of set vs doing neither.
Personally I love heat treating and do it to almost every hickory and black locust now I make. Heat treat does great things with black locust.

Kyle

Heated treated the molly.  I really like what that did for the hickory.
I also put a strip of rawhide on the back.  Propably didn't need to , but it was nice to experiment, and I would definetly hear about it if the wife's bow broke the first time she shot it.
I need to redo one of my nocks that didn't glue up correctly then it will be final tiller.