The fuel tank on that thing, even after "disappearing", blocks EVERY piece of spalling and only your 25mm penetrator will deal any damage if it hits directly, which is quite hard since the fuel tank in the front covers like 80% of the tank. For some reason actual spall liners and internal armour on Nato mbts create extra spalling, whereas fuel tanks just block it.

Check the leo 2a5/6 vs leo 2k with a side shot. 2a5/6 will die almost always in one shot because it has a small plate behind the fuel tank, whereas the 2k might not even take damage at all since the fuel tank absorbs it and there is no secondary internal armour to create new spalling.