Can felt products really scratch and clog into the earpiece grille of a smartphone?

Question

iPhone

For half a year I wore an iPhone 7 Plus in a case made of felt and leather from the HANDWERS brand.
Relatively recently, I noticed that the acoustic speaker grill was clogged, I didn’t pay attention .. A few days later, when I played music through the device’s speakers, a sound engineer friend said that I had phonitis , checked it turned out that the device did not fall from the upper speaker (auditory)
, it was always worn in a case, there are not even scratches, except for micro-nano, which are visible under a magnifying glass.
I honestly don’t understand what kind of nonsense ... There is no information on this subject on the Internet, I’m the first one to fall for such an absurdity ..
I eventually replaced it with a new one under warranty, the examination showed that everything inside is ok. But they didn’t tell me whether it’s felt or ordinary dirt, on the other hand, where does it come from, it’s always in a case ... Even while charging .. It doesn’t lie so that dust gets there.
Maybe there are people who understand this material and tell me?
I'm a perfectionist and little things like this piss me off :)

Answer 1

It depends on the quality of the felt , but in general, yes, it can.
(How boring I live!)

Answer 2

I was given the following answer from the tailoring factory:

Scratching - I think it depends on the softness of the felt, on the density and thickness of the hairs. Soft, plastic (made of fine wool) is unlikely to scratch. The only thing is that some kind of sticks, or thick hairs, usually get into the structure of the material, but they are usually visible and can be removed with tweezers. And if the felt is rough, all of thick wool (as for felt boots), there is even more debris in the structure, as a rule. There is also polyester felt, it also happens to be different.