If the avatar root scale is not 1.00, avatar become unexpected size.
Probably the avatar scale is forced to change to 1.00.
In the screenshot case, for example, root scale is 0.19 in Unity, but in OpenBeta VRChat, it became too large. It probably became 5.26 multiplied size of current size. (1.00 / 0.19 = 5.26...)