A person that repairs AC systems for a living would have to be an idiot to recommend a Stop Leak product, it would be the same as sending a client to another AC guy
They should say its bad and ruins the system, if they are smart
So grain of salt on what they say about those products
Been thru the same with Stop leak products for cooling systems, or head gasket leaks, products do work for SOME leaks but not all
And "trans fix" for automatics, swells gaskets and seals to get pressure back up(internal leaks) and does work for some issues
And no harm done since you would flush the system when doing a proper repair
They are all just temp fixes, and no professional mechanic would or should recommend any of them, its not in their best interest to do so
Back a few years, I got a stone chip in the windshield, had read about using a resin to fix it, asked my local glass guy about it and he said "NO WAY, windshield is structural, its the devils work you are asking for!"
Now, fixing chips and cracks in windshields is one the biggest parts of his business
I asked about what he had said before, and he said "well the product is better than before"
If you are a professional then you need to protect your profession, so grain of salt