This issue was mentioned by Franada as the sole reason for the T-pose layer still existing in Gogo Loco. Please ask them for more details because I do not really know much about this other than what they have said.
When asked about what the T-pose layer is for:
> fix the slight x offset the unity tpose have
> that the reason when you bind you feel a little shifted on the side. the tpose fix that
...
> but vrc could havea proxy tpose to fix it yes