While some of the others may have been a bit abrasive, they are right to question it.
- Generally after brazing, you should be pressure testing at 200-350 PSI, since those are the pressures R410a runs at. A good installer will usually pressure test for at least an hour, ideally overnight.
- Proper vacuuming/evacuation of the system really requires a micron gauge - not a gauge set. You should achieve <500 microns of vacuum, and it should hold at that level when the vacuum pump is turned off.
- Proper vacuuming takes really about 45 minutes to an hour. It takes a long time to boil any moisture or other unknowns out of the compressor oil and other various components.
So it just seems a little unlikely that everything was done 100% correctly if this was a full install, including the air handler. Assuming the pressure test was at least an hour, and the vacuuming was at least an air - that leaves 3 hours to do a full install of the air handler, condensing unit, wiring, ducting, brazing and insulation. That all sounds a little unblievable - especially for a first timer. The picture of the 100 PSI pressure test, and no vacuum gauge in sight sort of adds to the idea that some shortcuts may have been taken.
I will add that I do agree a lot of HVAC "pros" are overly secretive of their craft.