Large Caliber High Explosive....

[Imp]

Without looking into the problem with reports like that is human nature, you actualy need proper facts the human mind remembers the good stuff n forgets the bad.

remember a report that the russians claimed quite a number of destroyed tigers and ferdinands at Kursk

Well it was the biggest tank battle ever they would have been en mass & Germans were heavily outnumbered its amazing they advanced at all. After all 6 shermans were expected to take out a tiger so no surprise here

The shell of this gun could penetrate any part of the Tiger’s armor and even cut the turret from the hull

Im sure it happened but just cause one lucky shot took a turret off didnt mean it was common. Tanks have likewise been incapacitated by even more unlikely opponents due to lucky shots or nerves of steel ones by units that should not have been able to touch them, turret ring drivers hatch etc.

"The shell cut the right part of the commander’s cupola. I was not beheaded because I had bent down to light my cigarette

Well I would guess that was an AP shell not a HE shell that did that as was the next shot as they got out n were not concussed.
Remember also most tank engagements in WW2 tended to be at about 300yds or less which from memory means the ISU-152 is quite capable of taking out a tiger IF it uses AP shells in game.
If the HE shell was so effective why would they bother with an AP one though there is no doubt spalling would have been a bigger issue back in WW2 than it is now. The Tiger MAY even have been more susseptable to it as it was made out of very high quality plate though I dont think so. From memory the field tests carried out against captured ones when first come across in Africa by Brits showed the plate was 1.2 times harder than the best brits had to offer yet showed no signs of staring or cracking, in other words it was hard yet not brittle which can be the problem with tough plate. This is one of the things that made the Tiger so incredibly expensive to produce it was really the first Tank ever designed as a tank killer & in typical German fashion they spared no expense.