But he didn't leave his feet to hit high. If you look closely at the frame-by-frame still photos of the hit Grz was crouched down low on contact. Morrissey never elevated at all until his lower body connected with Grz, and it looks like he might have actually sort of stumbled forward off of his feet after contact.
Here is the sequence, in 1/10th second increments...
If you look at the last picture just at initial contact you can see that Morrissey is on his feet and Grz is in a low position, after quickly pivoting towards the boards (after Morrissey is committed to the hit). Morrissey didn't leave his feet to hit, nor did he hit Grz "high". Grz was below Morrissey's shoulder before contact because he pivoted and sort of lost his balance.