The backlight of MOTOROLA MOTO E6S does not seem to use PWM for the backlight

I tested it with a photodiode connected to the microphone input of the sound card. 

When I position the photodiode towards the phone's LCD dispaly I do not hear signs of PWM.

When I position the photodiode towards my LCD monitor Acer S222HQL Abid I hear about 1kHz beep (this is to confirm that my setup is correct).

Here is a photo of MOTOROLA MOTO E6S:

I am posting this MOTOROLA MOTO E6S image because this way my article will be better indexed by search engines. And may help users searching information about MOTOROLA MOTO E6S (if PWM is used for the backlight or not).

Another photo of moto e6s:

I am using these devices (stylus pens) instead of my fingers because I don't want fingerprints and dirt on the display: