It could be that GZ was talking about gaining control of TM's hand (presumably right) with his left hand. Keeping it out of his face as TM's other hand reached for the gun (or so he believed).
No, it could not be.
I don't understand why you are muddling the issue with this, after posting the quote yourself.
It was in the last interview, and Serino introduced the term 'wrist control', implying that it was law enforcement jargon. He was obviously referring to Zimmerman pinning Martin's wrist with his right arm, as he demonstrated in both the reenactment and the CVSA video.
Zimmerman answered without using the term 'wrist control'. There is no question of what Zimmerman was talking about when using the term, at least in the SPD interviews, because he never did.