To be fair, a lot of 60s war films suffer from 'stick a cross on it' disease
The Big Red One is a pretty good film, but the use of Israeli super shermans for tigers at Kesserine pass is a bit iffy. Can't remember what they used to represent a tiger in the Sicily scene, but I do recall it wasn't german, or indeed WWII vintage
Likewise a Bridge Too Far is quite good. Postwar Leopards doing Panther impressions aside
I guess it was just the case that there was an abundance of surplus kit about when these films were being made and people were less picky in those days about the equipment used. Especially if you are filming in the US where there was easy access to hundreds of shermans M3 HTs etc, and next to no real panzers.
Chris