Sounds like he lucked out and got a series of worn out pumps and gears or else his rods and mains are near shot.
If you have reason to believe otherwise there is a pressure adjustment screw on the pump body on early 54 and earlier pumps. You can turn it in a twist or two and see if that helps. Later 54 - 57 pumps have no such adjustment mechanism. If that is the case replace the by-pass valve spring and the by-pass valve. OR---you may have cracked a feed gear key or the key in the cam case, or one of them fell out somehow upon assembly.
Finally, just remember that pan oil pressure isn't much to write home about overall and never has been. Thirty some years ago I put a temporary oil pressure gauge on my 51 EL, shortly thereafter 51 pan "UL," and cold with 60 weight Valvoline it read about 35 psi. It dropped to somewhere from 10 - 12 psi when warmed up depending on who knows or cares what. That rattled me so much I finally removed the gauge, AFTER I realized that the bike ran just fine and has ever since with the same 51 pump. I noticed you didn't say anything about the engine not running right or making off the wall internal noises indicating mechanical failure due to lack of adequate oiling.
Peculiar to your specific engine, you might also have a bad pressure sending unit which stays lit all the time, or a bad pressure gauge. I have come across both over the years, but generally not at the same time. Maybe you have exceptionally bad luck, but as the manual says, normally the 55 - 57 pump is comparatively trouble free and the pressure is preset and non-adjustable. I assume you are using real HD pumps not aftermarket junk.
New Knuckleheads? Thank, you, Jesus!!