But even if this is the case: They ought to just use the Comet for both tech trees. They really shouldn't be using fantasy vehicles to fill rosters as you're suggesting...
And that's where we're just going to disagree.
Some more variety with units that are only one human decision to ship away from seeing combat is fine.
BP is not a fantasy. The Ratte is a fantasy. The BP is a real bit of kit available from January 45 that just never got moved to the frontline.
But it could have been.
And so, in a campaign where we have some freedom to choose how we play out the war, is fine.
There's also, as has been mentioned, the 75mm Churchill.
Anyway, instead of using the BP they could instead simply use the Challenger, which WAS actually used in combat. I refuse to believe they're going to have three separate tech trees that all require an "unique" 17-pounder toting medium/heavy tank.
The challenger is a medium, and would not fit the heavy lumbering aesthetic they have clearly gone for specifically with the Armour Company.
The 75mm would cause all matter of wehraboo whining if it was given the same punch as a 17pdr would about how the gun is overpreforming.
And not all of them need to end in a 17pdr. But they should all end with something. Asymmetry in basic toolkit is bloody awful for the balance and was the cause of years of overhauls and balance issues in CoH2.
I assume (and we need to wait for it to be out of pre alpha to see) that the list will include the BP, maybe the Crocodile, the Comet. All three of which we know to have existing models.
Royal Artillery has a larger than usual field gun instead, so it's not all heavy tanks, but it is all late game units.
Recycling the same vehicle a dozen times over in marginally different commanders to pad the roster is not good game design.