I learned of the lid angle sensor due to my MBP draining its battery. Whenever I flew across the country I'd always end up with a dead battery. Originally thought it was some process preventing sleep but was spinning circles hunting it down until one night, I closed the laptop... the screen turned off as it was closing and just as it shut.. you could see the faint glow of the screen turning back on again. If I cracked the lid open 1/8th of an inch it would turn off again.

I had thought that the MBP (an Intel one) had used magnets to detect lid closure but alas that's when I learned of the lid angle sensor and all the symptoms I was experiencing made sense. Basically the laptop would wake up when shut and the screen would stay on the entire time thus draining the battery.

Ended up getting the LAS replaced which was not DIY'able unfortunately... but was a relatively cheap fix (~$90).