I fully support independent repair shops but I am willing to pay more for a quality job. Right now since Apple doesn’t certify third party repair shops, there’s just no way of knowing.
That's exactly what the AASP program is.
Isnt that like a car mechanic, there are good ones and there are bad ones, you need to find the good one or you can go to Apple if you dont want the hassle.
The issue is when "sub-assembly B" costs hundreds or thousands and the actual "defect A" is due to a loose connector or a cold solder (or whatever else easily repairable), the dealer will go by the book, an independent mechanic (if he/she is actually "good") will fix it for a few bucks.
Compare with the re-known cases of motherboards replaced because a connector pin was bent or similar, there are quite a few related videos by Louis Rossmann.
Same experience with $2 tempered glass screen protector I've got on yesterday. Also typing accuracy massively decreased.