Possibly the problem with the Luftwaffe claims is the same as the problem with US bomber claims, that is every bomber claims every fighter that is hit (as well as some that produce smoke when accelerating). Perhaps if everyone fires R4Ms at long range, any hits (and any random FLAK bursts) are reported as kills by every Me-262.
At first sight, calculations suggest that there should be at least one hit per Me-262. Even the problem that aiming the Me-262 was difficult due to snaking (also a problem with the Meteor and the P-80) should not cause it to miss a bomber box as the rockets were launched in four sets with a 0.07s delay. However, that does assume that the range is estimated reasonably correctly. The initial intention was to fire at 1500 m (outside of gun range). Experience caused the range to be reduced to 600 m (from the side an Me-262 closed about 200 m/s). Initially even aces were beginners with the R4M (Galland forgot to set the arming switch in his first attack). Thus it is possible that over the long month of R4M use, there was some improvement in effectiveness. Note that the USAF copied the design and trained to hit jet bombers in head on attacks at night!
For my Alt. Hist. idea of using R4M equipped Me-262s from February 1944, the Luftwaffe would have been able to train against towed targets (say over Silesia in January 1944) and I suspect that they would have started out hitting on most attacks. A radar for ranging might have helped but with practice the rings on the Revi should give the range. Manufacturing problems may have caused some R4M to miss in 1945 but that would have been quickly solved in less chaotic conditions (if it was a problem).