He was so desperate to take one that a terrified teenager ended up taking the walk from the centre circle for the decisive kick, all because big bad Gary Southgate forced him to do it.
If he's looked at the volunteers and decided that Saka was the best bet for that pen, it's because Grealish stood there meekly saying "I will" and shitting himself stupid when asked if he'd take one.
The fact that in that scenario Southgate chooses Saka over JG, for me, is more damning of Grealish than Southgate.
As for Grealish, he ought to wind his neck in and go back to faffing with his alice band and miniature shinpads if he wants to be in the WC squad, as that comment, however he's tried to dress it up, is shunting all the blame onto Southgate, who has already admirably taken the the burden himself IMO.
Again, I'm no Southgate fan by any stretch, he's a decent bloke but very limited manager, but I think he's been let down big time by some of his players when it comes to the pens. The 120 minute back 7 clusterfuck that preceded it though is all his.