The issue isn't necessarily weeding out the bad shops, although that is important too.  The issue is keeping bad situations from developing despite everyone's best intentions.   It would seem prudent for repair shops to adopt those procedures for their own protection as well as the customer's.  They don't need to have their reputations sullied because of bad situations that arise from poor communication.  Those are often situations where the fault is distributed between the shop and the customer.

There's no real reason instrument repair shops can't use the same best practices that are common to auto repair shops.  Most common repair items aren't that difficult to diagnose at the outset.  If there's a severe issue with build quality, wear, or previous work, those tend to become obvious pretty quickly.  There's often a choice to be made - do it the best way or do it the get by way.  The best way might not fit the customer's budget and they need to be kept in the loop. 

Customer experiences for any given repair shop are often all over the place.  It's situational - type of work, customer's budget, time constraints, etc.  It's important to get all of that out into the open at the outset.