As said, I dont think anyone doubts it happened. What I doubt is that a gunner could arrange his show to go in that matter without providence a significant amount of luck on his shoulder. Is there anyone that could boast they did it more than once?
Yes - well, not the bounce but the ability to hit a very specific target with a tank gun at normal combat ranges.
A certain L. R. Price from APG, who was a civilian expert on the 90mm M3 gun, gave a lecture on boresighting of the 90mm gun at Aachen in Germany in February 1945. He showed the gunners that the 90mm gun was sufficiently accurate that gunners should not"...just aim at the enemy tank, but to aim at a particular spot on that tank and his demonstration showed it was possible to hit that spot." Later, he used German steel helmets as targets, picking the off with the 90mm at 625 yards. "...veterans rapidly duplicated his markmanship, once they got the feel of the weapon."
Source: Hunnicutt: "Pershing" p. 16-17
If you believe that then you have to believe that the tanks of the US military, tank cannons, and ammunition have become less accurate over the last 70 years.
Maybe Price was just a better gunner than you.
Anyway, the point is:
- The Panther mantlet bounce was possible and it happened from the Panthers first time in combat
- For most allied tankers, trying to hit the lower half of the mantlet was a much better choice than to try to hit any other part of the Panther. And if more gunners try that, more will succed, even if the chance of achieving it is small.
What seems odd to me, is that people seems to think that allied tank gunners in WWII were just blindly firing in the general direction of the enemy. And the assumption that they could always just "move to get a side shot" or something similar. That shows a distinct lack of knowledge and understanding of the WWII battlefield. It probably comes from trying to fit a 1940ies reality to a 1970ies or 80ies experience, something which amateur historians among modern soldiers often do.