Why does my 2012 MBP respond to the NFC on my phone?

[Danzuran]

When I place my Android phone with NFC against a specific part of the area on the left of the track pad the Mac goes to sleep and wakes when I tap it again.

 

[/V\acpower]

My best guess is that there is some form of "magnetic field sensor" at this area that detect when the laptop is opened or closed.

That sensor is probably just fooled by that NFC field.

 

[New_Mac_Smell]

They used to (Might still do) use little reed switches, as most laptops do, on the lower part of the body. With a magnet in the upper part. So that when the lid is closed it knows it's closed.

As above pointed out, it'll be because of the NFC magnetic field.

I'm more curious what you were doing to find this out?

 

[andy9l]

Magnets: https://support.apple.com/en-gb/HT203315

 

[Nik]

Your smartphone is an active NFC device -- it's using power to generate a magnetic field which triggers the sleep/wake sensor of the MacBook.

Mystery solved.

 

[maerz001]

It's triggered by the magnets of the loudspeaker not NFC.
It happens with every phone even without NFC