You can of course set it to something just slightly smaller, e.g. 16380.
The key part is that as long as we don’t need 32 bit indices for the index buffers.
I wouldn’t have thought that we actually changed this, but I’ll double check the code to see what could cause this.
EDIT: Looking at the code, it was the introduction of the sprite trimming that increased the number of (possible) vertices for a sprite from 4 to 8, hence the change in behavior. It was not intentional, and I’ll look into a fix tomorrow, for the beta.