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?