The young rec who overbet-shoves the river after calling two streets has a polarized range that's heavily weighted toward the nuts, not a bluff. They're not sophisticated enough to bluff-overbet.

Why they do it

Young players at $1/$2 who have been watching poker content know overbets exist. What they don't know is when to use them as bluffs. So when they overbet, it almost always means they just got there. The draw completed, the set filled up, whatever.

The adjustment

Unless you're at the very top of your range, fold to the overbet shove. It feels like you're being pushed around but you're almost always behind.

What it's worth

Hero-calling an overbet shove with two pair costs you a stack. One correct fold here per session is worth $100-200 in EV depending on effective stacks.