Just to nerd out a bit: I think this is justified. He has nanomachines, son. His eyesight is probably perfect, but he adopts a different persona most of the time. He’s a puppeteer and a politician most of the time.

This is when he gets his actual boss theme lyrics too and he finally treats you as an actual fight. No more metal gear, no more speeches. You get the treatment of an equal rival.

Or: Rising Revengeance might like symbolism, but it prefers the subtlety of a giant boulder and memes, and him taking off his glasses just fits the rule of cool.