His words, said 'I will' in some context or another, might not sound like much but there is a difference between volunteering and saying that when asked.
I just can't see Southgate having Grealish throwing himself forward on one hand, and Saka bricking it on the other, and forcing Saka to take it.
Order was pre-determined by Gary before the game..... Gary asks each at the last minute "you still up for it?"..... The same 5 accepted.
I don't think anyone has claimed Saka was "forced" to take one.