I just watched it again. This particular holster has a thumb release, near the safety of the gun. (not an issue for you, on your model)
But there's also a release just outside the trigger area, it seems. His gun didn't draw smoothly because he didn't trip both releases (if I understood correctly) and when he pressed the index finger release, he forgot to keep his finger straight. His finger then went into the trigger loop and BAM.
I don't think it'll be an issue for you, as M&Ps have longer trigger pulls. I don't think a holster with more than one thing needed at a time to release it is a good idea.