The issue there was that number of layers did not include normals,
while element size counts bytes used by normals. This sounds very
fragile and dangerous to work further. Also, one value can easily
be delivered from another, so it is redundancy going on here.
Possible difference now is that multires subdivision will copy
normals to a higher levels. Shouldn't be big of a problem, since
leaving old normals and updating coordinates is not correct either.
Sergey Sharybin
94ec80d21c