Steps to reproduce :

1) open the graphics speed panel, see the fps while wearing the hair

2) detach the hair

3) observe the fps raising up (up to twice the fps in certain cases).

observations:

note 1: i'm using the graphics speed panel to show the fps because the statistic panel by itself would drop the fps.

note 2: this seems mac specific (maybe Apple Silicon). The issue doesn't occur on windows PCs with different configurations.

note 3: in the graphics speed panel, in avatar complexity, the hair is shown as being the attachment with the less complexity, strangely. this might be a measure glitch .. or might lead to some answer.

note 4: this is happening in SL viewer since pbr, and all other pbr viewers betas. this is not happening on pre-pbr viewers.