What does pressing ESC at POST screen exactly do?

[lindycogito]

So what does pressing ESC at the POST screen exactly do for Thinkpads? Not sure if it depends on the model / BIOS; but in my case I am talking about a X61 tablet. F1 is for BIOS setup; F12 is for booting devices list; so what does ESC officially do?

The reason I am asking is that it mysteriously solves the 'thermal sensing error' which would normally prevent booting (as described in this post here) -- I'd like to try to understand a bit better why pressing ESC could help...

[rkawakami]

The only things that I know happens when pressing the ESC key during POST is that the boot diagnostic messages are displayed and the system EEPROM is unlocked for writing.