We have a number of shops that use it this way against my advice but the smartest shop who has been doing this for 15 or so years says;
Each painter (3-4) averages 1-2 come backs per year where there is a problem BUT they make money redoing because of the time they save on all the jobs over the year.
To sum up they are a dealership and as he points out, facts that show if you wreck you car 97.7% of the people will not own in 3 years, so minor gamble for him, also they are just doing small repairs, so when one comes back, its usually one panel and a finger print bubbling.
If a restro shop wanted to do this, I would tell him to use someone else product ALL the way through the job, so I don't get blamed.