It is pretty awesome that they have an actual Tiger in action, and not just a replica! That is worth the price of admission alone IMO. Good catch on the Sherman model. I'd ascribe to your theory that the crew's Sherman was slightly out of date. Not impossible that a more obsolete model would be used to buff out the ranks. And I could imagine the crew having that affinity for it. They are supposed to be veterans of several campaigns, right? In reality, any tank crew or commander having survived the war for any length of time would likely go through several vehicles like my kids go through shoes.
I can totally appreciate your desire to gush about the movie. As soon as I see it, you'll know! Probably will write a journal to fish for everyone's opinion.