Maybe I don't know exactly what cliff vesting is, but while Microsoft doesn't backload vesting, it does do vesting in chunks (like once a year iirc). And as another commenter pointed out it doesn't kick in until 6 months. But at places like google the vesting is monthly and starts after the first month.

Also one quirk of microsoft is since they have a half-title promotion system, as I understand it, it's normal to get refreshers on years 1-3 through a 4 year vest after a half-title/one-level promotion.