This is not consistent with the information I've heard, which I have good reason to believe is accurate. The information I have access to is specifically that lighter tanks are surviving better "pound-for-pound", by which I mean, adjusted for equivalent circumstances, and as a proportion of the number used. I acknowledge that I can't prove this, but my impression was that this is widely known.
Maybe if you post your sources it would be easier to explain to you why this is absolutely, categorically, wrong. What you're arguing is something that theoreticians believed roughly sixty years ago, but which was abandoned after only a single vehicle generation (represented primarily by the Leopard 1) because exercises and reports from combat zones (primarily late-era Vietnam and various wars in the Middle East) showed that older vehicles with heavier armor routinely had greater chances to accomplish their mission than lighter ones. They were also much more likely to be able to be repaired and returned to service if knocked out, and the crew was more likely to survive.
Of the more modern, heavier vehicles that have gone into action, far fewer have been knocked out in proportional terms, not just absolute. Of those that have been knocked out, the vast majority have been repaired and returned to service rather than ceasing to exist.
Your comparison to the M4 Sherman (or T-34) is fundamentally flawed, because it was
not a lighter tank compared to the main German equivalents. The Panzer IV was of similar size, and mostly struggled due to be obsolescent even at the start of the war (this is not Germany's fault, tank technology just advanced ludicrously fast by then and the Sherman was about four years newer. The Panzer V "Panther" was heavier, but the generally poor (yes, poor - the early engagements heavily favored the Panther because of the terrain, but that did not last) performance was due to significant design flaws*, not the size. Eliminate those, and the comparison looks far worse. The Tigers generally were irrelevant in this comparison, as they were not a M4/T-34 analog. They were the equivalent of the KV/IS series, or the British Churchills, primarily intended as heavy assault vehicles to punch
through a particularly tough defensive line rather than outflanking it.
*For the interested, the big flaws were pathetic side armor (prewar AT rifles could punch through it), an excessively large gun (it was capable of punching through almost Allied armor at a distance of a kilometer, and most at 2, but such shots are so extremely rare that having that range is essentially wasted - it would be better to settle for punching through most armor at 500 meters and enjoy a much lighter weapon) that fired excessively large and heavy ammunition (rate of fire was drastically slowed, and the loader fatigued easily), extremely unreliable transmission gear (though not as bad as the morbidly obese Tiger II), and absolutely terrible visibility for the gunner (he only had a telescopic sight, while a Sherman (or Panzer IV!) gunner had a wide angle periscope, which allowed him to readily find a marked target instead of having to be coached by the commander),