Only way to be sure you don't leak confidential data is to destroy the hardware, companies like this have been destroying hard drives for a long time, they hardly ever resell them, with new laptops there is no separate hard drive + there is other sensitive data outside of that.

They could organise to sell the computers without the motherboards to repair stores possibly, that way people with broken screens may be able to swap in a motherboard etc, but i doubt the recycler wants to do that work.

If the recycling company sold these locked computers instead of destroying them to a bad actor who sites on them hoping someone finds a way around this lock they would sued into non existance.