People have it in their head that he'll get bullied because of his size, so every time he doesn't play well they'll twist what they see to fit that narrative, even when it has little or nothing to do with that.
In this case he just straight up didn't play well, in exactly the same way any other CB making a step up to the PL with little pre-season next to a CB partner they've never played with before might.
People fretting about Ivan Toney is ridiculous. He's 5ft 10, an inch taller than Martinez. By the same height-is-everything logic applied to Martinez, he
can't be that dominant in the air.