Well here is an experience with a Tecumseh OHH60 using a lead down tester.
The engine comes in with a bad carburetor (water damage) and busted fuel tank. Test fired the engine and did a leak down test with the leak down indicating only 20% leakage pass the rings, no other leaks indicated. So I order a new carburetor and fuel tank. Once I got it running it was smoking a like freight train. I found oil in the intake after the carburetor indicating a bad intake valve stem seal. No biggie just install a new seal I thought.
Well that only reduce the smoking. Btw the valve stem seal did fix the intake oil problem. Normally we do leak down tests at TDC compression. I decided to disable the valve train and test BDC. Boy what a difference in leakage rate as it went to over 60%. Well I got a new engine installed in it place so I decided just to see what actually was wrong the Tecumseh. The cylinder is so worn that it is already at 0.020 over with the piston easily moved side to side in the cylinder. Too bad only .010 piston and ring are available as I would need do 0.030 over for this one.
Just proves even with good test results using test tools as indicated still will not find all the problems with a cylinder. I probably would had been still scratching my head if I didn't try a secondary leak down test.