Don't they listen to their own LPs?
That's a fascinating idea!
Frankly, I am horrified when a record store offers to play my new record to check for defects
. Doing so would immediately turn it into a second hand item in my view!
Most likely they would use a DJ-style deck with an unknown amount of stylus wear. If played through loudspeakers, they would risk emptying the store of customers (Mahler is not for everyone, after all). The noise floor of the store may exceed the defect level and most headphones are not that revealing.
I have no objection to manufacturers sampling their output, provided the samples are not sold as new. Sampling can show overall trends - like the wear on masters - but obviously cannot detect every faulty record.
In reality, I think manufacturers expect a return rate and factor that into the cost of doing business. What they don't seem to factor in is reputational damage. But apparently most records are bought by people who have no means of playing them anyway. Of the six sets (12 disks) of Mahler 2 sold by my record store, only one set has been returned so far.
Deutsche Grammophon (DG) in Europe seem to have a new tactic to reducing returns. They don't supply in the first place.
I am still waiting for Rachmaninov Piano Concertos ordered in January, and recently released Paganini ordered a month ago, all from Presto Classical.
Presto are particularly responsive and helpful. The have refunded my money on defective records from DG's sister company Decca after asking for photographs of the damage. In one case, it was obvious from a line of detritus caused by abrasion from Decca's new, glossy, thick, carboard inner sleeves. In another case, it would probably have needed an electron microscope, which requires destruction of the record. Presto asked me to destroy the record after getting my refund which seems reasonable especially as I bought the CD in the same purchase. Never had to return a CD ...

