I have a dive buddy (we've been friends for 40 yrs) , who's not "technically" an instructor, but he's a Sat-Rat on the Hibernia Oil rigs. He showed up at the house one day, with 2 Draeger Re-breathers, Kirby-Morgan dive hats (complete with voice-gear) , and said "Come on, we're gonna do some "Real" Wreck diving today. Off we went to Brockville to dive the wrecks.
Being used to 1 hour dives; it was totally new to me, to be doing 1 hr Decompression stops!!!! He monitored me (including that I was comfortable), my gear, and our dive times using his skills that he's learned over the years.
So bottom line... This guy is not an "Instructor", he took an "unqualified diver" deeper than they had ever been before, using equipment that I had never seen; and yet I felt SAFER diving with him, than with many of the "Instructors" I have dove with at other destinations.
IMHO, You can have all the "pieces of paper" you want, but it don't mean crap, when it comes to real world experience.
Thoughts?
There are benefits to finding a mentor who is more qualified and experienced than you are that can share their knowledge with you and make you a better diver.
This is not one of those cases.
Tech instruction generally starts off on a gradual curve, adding new skills and building on those before taking the next step. This ensures that divers have the capabilities of handling things that may go wrong and some instruction on what those dangers may be. There is no course that I know of that throws you straight into a dive with a 1 hour decompression stop.
What happens if something had happened to your friend? Suppose he had a medical issue or passed out from one of the 3 H's of rebreather diving? Did you know enough to get him, or yourself back to the surface safely?
Is formalized training the only way to learn? No. But that doesn't mean this was a good, or safe, idea either.