As far as i can tell the document says > 360mm of perferation. So while in line with what Warthunder statcard has (it being 400mm, which isn’t outside impossible based on what that document says) , this could probably be reported to be fixed if one wants to.
No, these got removed because they are complete fabrication as to how they are shown in game.
In your own screenshot, it’s apparent you haven’t even played it.
If you did, you might appreciate the massive size which makes it difficult to hide, the bouncy suspension meaning you can’t flank effective, the paper thin armor which lets even AAs through from even frontal arcs, the mediocre speed that sees you outpositioned by other mediums, the very inconsistent post pen damage that 105mm HEAT offers, and just generally that penetration is not the only stat that matters.
That you’d even compare it to the Leopard (based purely on the HEAT pen alone, I assume), shows how little you appreciate about these tanks as a whole package.
The M51 with correct damage could perfectly be at Br 7.0 or 7.7, since that HEAT model was very powerful. The problem is that from the beginning the bullet damage model has been a disaster, and if you add it to tanks that carry bullets that they never used, causing there to be many cases of tanks with a Br that does not make much sense.
Even then I doubt it would go higher than 6.3 or 6.7.
All other disadvantages still apply to the vehicle that other users have already mentioned. Especially at 7.7 the vehicle would be utterly outclassed by it’s competition.
Then again, the M-51 being moved up for an improved damage would imply other heat slingers would move up as well, but that just makes it a “what-if” that we have too little data onto imagine what such a game could look like.
Keep in mind that with that HEAT the M51 can perfectly destroy any tank up to almost Br 8.3, the only thing that happens is that because of the damage model in many cases you need many shots, when in many cases the first one should already be completely disabled , and dead from a second shot.
On the other hand, adjusting the damage would not cause any problem, it would only be so that the WW2 tanks could finally be separated from the post-war tanks, since the game is as it is because of the damage model, that is why we see the Tiger 2 vs Ratel with ATGM.