I'm not sure what Manning was getting at here, or what he was trying to prove. I'm assuming he's just talking about how he just adjusted from play to play based on what he was seeing, but some people aren't great at that.
When I coached halftime adjustments were a massively real thing. Seems like they were for Nick Saban, Kirby Smart, and Urban Meyer as well, at least they reference them in these articles:
Head Coach Nick Saban Opening statement "I think there are some lessons to be learned today. I think when you're not mentally ready to play a game, you don't...
rolltide.com
ATLANTA — The final score made Georgia’s 34-3 win over Clemson look a lot easier than it really was, and Kirby Smart knew that.
www.dawgnation.com
Urban Meyer's adjustment from college football to pro football includes adjusting to an intermission that's 40 percent shorter.
www.nbcsports.com