Why? Nejire's attack actually injured him and left him a bruise. Mirio can't even hurt Shigaraki period, he can't even hurt or move the Near High-Ends. While Nejire is shown to be capable of forcing one into the ground. If you punched someone in the gut and they're visibly bruised, you can't scale to them at all?
Mirio stated he was escorting Nejire's energy to him. Mirio added nothing to that punch, he's vastly weaker then her in terms of power.
Nejire's attack have zero mention or showing of being heat based either. Which means she did leave a sizable bruise on his body. If the attack actually drew blood, a blunt attack mind you, that'd imply the attack was stronger than his durability. Which would be very absurd. Mirio isn't scaling, but Nejire just got very clear scaling.
@TimmyTurnero
There's no point in discussing Suneater's attack until we see what it actually does. Best to hold off until we get actual clarification.
Nejire's AP would be High 6-C (Baseline at worst).