As an aircraft mechanic I've done lots of these, the publication AC 43.13-1b outlines the correct procedure. The test is done on a warm engine and, to start the test, air is introduced into the cylinder while the piston approaches TDC and is finalized with the piston at TDC. The airplane has an advantage because of the prop, you can grab a prop blade and manipulate the piston position instead of just parking it at TDC. This assures that the ring is fully seated against to bottom of the ring land.
That is interesting, and makes total sense. If you have a balancer that is marked every 90 agrees and you do your leak down test following the firing order you should be good on this aspect as long as you don't pass the mark and back it up.
