RV-12 owners who are adjusting their propeller pitch and actually flying their airplane usually learn quickly that the accuracy of the degree value on their tool is not important. Since most people adjust pitch based on what they see for cruise RPM / airplane performance, all that matters is that the reading on the tool be repeatable.
All of the digital levels I have used, regardless of their specified tolerance, have had very repeatable readings. I.E., you can set them down on a fixed / non-movable object (specific spot on your shop floor) for years and it will read the exact same value every time.
So, as long as you use the same tool, and the exact same procedure (always position the digital level on the blade measuring tool the same way, etc.) the measurement value is very repeatable. At least close enough that removal of the prop and re-installation to a specific measurement results in the same max. RPM in the same flight condition, and in this situation that is all that matters.
In the end, we don't need to know whether the pitch value is 70.8 degrees or 70.9 degrees. Only that we know how much change we made, or that we successfully adjusted back to the same # that we were using previously.
As mentioned, if the digital level is always zero referenced to the cockpit side rail (recommended in the RV-12 documentation), then it will never matter where the airplane is sitting when you are adjusting the propeller pitch. You could do it parked on a hill and your desired pitch value (hopefully recorded in your log book) could still easily be set.
BTW, the tightening order/process of the hub bolts does have an influence on the blade angle. as you alternate back and forth on the bolts while tightening, it is rocking the hub back and forth as well. This can move the blade angle very slightly. With practice, you can use this to your advantage as you are coming up on full torque by adjusting your tightening sequence slightly to get the blade to go that last tenth of a degree towards the value that you want.
Because very few digital levels read in hundredths, even if you have the exact same value on both blades there is still a potential for there being a .1 to .15 degree difference (set your digital level on a hard surface and see how much you can lift one end before the value changes to the next tenth). It is for this reason that I always strive to get both numbers the same. Experience has shown that if I do, the level of smoothness is worth the time.
I can set up the blade pitch on an RV-12 in 15 - 20 minutes. I have had some practice
but this is attainable by anyone with practice as well.
One important thing that helps a lot is devising some sort of tool that can be hooked on the blade to give you more leverage to rotate it. Our tool is about 3' long. The additional leverage provided by the tool is what allows for making a very small movement in the blade pitch