I hate to be that guy, but why in the world would we need to call this 'microinteractions' instead of just interactions? Why do people feel the need to overcomplicate the field with useless terminology that adds nothing extra, except the terminology itself? Small or big, you better just make sure you design your interactions well.
Completely agree. However, I do feel that in this particular case 'microinteractions' works well because it speaks to the small, minute details that he's referring to. You probably wouldn't refer to them as such to an everyman, but then again, thank God we're all 'designers' on here right? haha