backlightTimeout and button behaviour

I can't help but feel there's something super obvious I'm missing.

What about the code example I posted? Surely that will work fine, without messing with the lock timeout?

it really does seem to be behaving like it's locked but it shouldn't be.

It eats the first press if it was locked or the backlight was off. Your backlight timeout is 10s so it could have been off.