This armor is too hard, even top-tier ammunition cannot penetrate it.

It is based on a modern tanks. The BMPT-72 (the one you showed) is based on the T-73B3 with additional relict era on the upper glacis. The vehicle was designed to fight in urban combat, so the designers of the tanks decided to heavily armour the ‘turret’ thing. It is this armoured due to the design of the tank, in other words.
As @Kyuss well explained and justified why the vehicle is a real tough nut to crack I’ll explain why the image shown states a possible penetration but in really that will be a very hard shot to go through:
BMPT and BMPT-72 as I’ll refer as Terminator to englobe both existing variants in-game is not a unmanned turret vehicle, as much as it looks like one, other examples are TCM AGS and KF-41 Lynx, meaning the Terminator is required to have a proper turret armor as there’s a turret with crew and electronics inside it.
For a true unammed turret you’re looking at vehicles like Schützenpanzer PUMA and Boxer Vilkas where the crew unlike the other vehicles mentioned is not directly positioned in the turret and relies on remote controls to proper operate the gun in the vehicle, which is justified by the tasks that the Terminator is applied on: armor.
In-game this same spot you shared in the attached image is misleading and behind this fake softspot for shooting there are layers of armor composite materials angled, it’s just a external structural part that gives you this false information that “There’s a weakspot here!” But in really it’s not.
Where did the actual defense data for this armor come from? It just happens to block the attack of the game’s top-tier ammunition. Is it such a coincidence?
As much as I tried to look and gather information, with little success, yet I believe it’s accurate in-game, BMPT and BMPT-72 do have a turret armor according to this diagram published in an article in Army Recognition website:

its just a russian hull why are you complaining so much
Magic Russian ERA that is designed to ignore physics/balistics in game
put the maus at 1.0 then its just a hull
Im bot saying that the info is wrong but im just surprised that flat part can stop DM53
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Yeah i’d like to know why terminator is the only new vehicle that i could find with variable thickness armour on the turret, when it’s clearly just welded armour plates.
And it matters when you compare germinator and terminator from temu turrets.
russian one has bunch of overlapping different thickness armours and the temu one is just 25.4mm everywhere, even the turret ring assembly that you can see is clearly thicker…
Makes you wonder where they get their sources for these classified vehicles from certain country.

most things are classified, so it’s most likely guesswork.
The difference is:
When NATO, negative guesswork.
When Russia, positive guesswork
A ray of hope for Garbage players
Exactly
Its is armored enough to not be completely destroyed by FPV drone. So far no video of it being destroyed
Edit: NVM found a video of it being destroyed by FPV
It might be because of the obvious russian bias put in place in the game, but we cannot say such thing here, so I’ll just say it’s because the BMPT is modeled quite well and realistically.