I don't know what to think about those Pro Press fittings. It's a single o-ring seal just like a Shark Bite. I'm sure they're fine enough, but I feel about that the same way I feel about burying a Shark Bite under my concrete. It'll might even last 15-20 years before you have to do it again.

...that said I have reservations about burying copper too. If it's in contact with the soil it should not be metallic pipe. Particularly old houses that grounded their electrical systems to the plumbing. My house was built in 1994 and I had four pin-holes in the copper pipes between 2009 and 2014 when I just got fed up and ripped all the copper out and replaced it with PEX. That was caused by a faulty clothes dryer leaking current to ground through the plumbing system.