Shortround6
Major General
There is "quality" in "quantity". The Germans often tried to introduce tanks (or other weapons) in small batches. A few mechanical failures and things turn pear shape very quickly. The Russians tended to use things in masses large enough that even a number of mechanical failures left a large quantity of "runners". If you have a large enough reserve of runners you still have enough tanks (or other items) to 'complete the strategic objective' a number of days later. One reason the Soviets had such a large number of tanks during the cold war was as a "reserve". They knew 30/40% of the initial wave would be side lined in about 4-5 days with mechanical break downs.
I am afraid this method doesn't tell us much about the individual reliability of the tanks.
I am not sure how a post war built submarine tells us much about a war time built tank. The Russians could build decent stuff at times. Build quality of tanks may have been much different in 1942 than in 1944/45. We know that "some" T-34s went into action with spare transmissions strapped to the rear deck ( no 360 degree traverse of the turret) which doesn't argue for high reliability. Later T-34s used a 5 speed instead of the early 4 speed, a different transmission might ( or might not) change things considerably.
No tank lasts 30-35 years if it is actually being driven and not being used as a gate guard without spare parts. Syrian T-34/85s were post war Czech built and there were a bunch more T-34 parts floating around in the 60s and 70s than there were German MK IV parts.