Compression numbers on a good engine (4, 6 or 8 cylinders; it makes no difference) should be in the 180-190 PSI range. If they’re telling you that 100-105 is good and acceptable they are horribly misguided to put it in polite terms.
If the numbers are 105 or 150 it makes no difference. A dry compression test should be followed up with a wet test; meaning each cylinder gets a small shot of oil before it’s tested. If the numbers jump up considerably then there’s a piston ring problem.
Every number in the process should be written down as the test is performed.
They may balk at pulling the pan but if the car were mine that pan would come off and a few bearings would be inspected; both main and rod bearings. I might add that any rod or main bearing caps that are removed for bearing inspection should be those located the fartherest away from the oil pump as they are the last ones in the string to receive pressurized oil. If those bearings are problematic then you know the ones closest to the oil pump are even worse.
Finally, I might add that sometimes those specifications (even in factory manuals) are incorrect. Blame it on slide rule engineers or whatever but those numbers seldom ever come out of the real world.