They mean someone who's extremely passionate about this could identify the car brand or exact model in question just by listening to the sound the lock makes from the posted video. You know, like the experts who can identify a wine by smelling it, or a violin just by listening to it.

Or a car brand by the door mirror shape.

he*

I wouldn't know, and don't want to investigate. I try to stay generic, grammatically it's fine. I'm sure it can be grating to some but I'm not using this as a trigger word.

it's not grammatically fine - you're talking about 1 person

The singular "they" usage is over seven hundred years old.

It's not hard to figure out the brand anyway. I don't know why he hid it in the first place. I'm all for name and shame.