Thanks for the question 
Hair today, as you mentioned, can be either rigid or layered, and today the accessory adjustment tool works for rigid accessories. However, both types of Hair are listed in the ‘Hair’ category on the platform., The concern on making just the rigid Hair adjustable is that there’d be different behaviors for accessories of the same asset type.
Our long term plan here is to make both rigid and layered accessories fit better, as @ Klaugrana001 mentioned. We’re evaluating a few potential solutions and would make Hair (as a category) adjustable once we have that technology to adjust layered accessories. Before then, we don’t want to deliver a half-solution that would only allow for adjusting certain Hair assets.
Thanks a lot for the question and your patience – hope this helps explain some of our thinking. Thanks.
-Charlie
PM, Avatar Team