Even if that's the case, that's a Windows bug and has nothing to do with UEFI.
Although, I'm pretty sure if Windows touched boot loader in an MBR setup, it surely would remove grub completely. In UEFI, it can just don't touch Grub's stuff easily; if it doesn't then that's its problem.
MBR simplicity is a lie! It is simple itself, but boot loaders are complex: Grub effectively has 3 separate stages (1, 1.5 & 2) to just run itself...
@0x4E4F
So, you are happy with MBR as Microsoft doesn't care about it anymore :D