> I've seen it correctly detect AI writing even when people use those "humanizer" rewriting skills

Those skills are meant for humans, not for models. Pangram said in their recent model update that they now also detect the humanizers.

All it requires on their end is running each of their AI outputs through each humanizer and including it in their corpus as ai-humanized.

It's essentially impossible now to prompt your way to non AI detectable text. Even if you do today, it'll be picked up by the next model update.

This is why in academic environments its probably worth re-testing old exams or papers periodically - same way blood and urine samples from athletes are preserved to take advantage of better future testing.