That's great, bit is still only a secondhand account of Stalin's opinion. I heard argued a lot that by the time lend-lease really kicked in, Stalingrad was already over and the balance tipped in the Soviet Union's favour.
Yes, that whole page may be biased, but Stalingrad was ‘only’ the mental turning point, but only after Kursk, 7-8 months later, was the German collapse unavoidable. Even then, lend lease didn’t contribute much percentage-wise, but it doesn’t take a huge amount to tip a well balanced battle.
Also, the allied landing in Sicily forced Hitler to move forces from Kursk, and that might not have taken place that early without land lease aid to the British.