It seems that the saves can't be entirely ignored even when starting from 7+ or when the armour penetration would bring the value to a number strictly superior to 6+. In every case, the formula seems to consider that damage can be saved as if the defender had a 6+ save.
Here's a screenshot (with auto-hit, auto-wound, 7+ save) :
We can see that the expected value after save should still be "1" but it becomes "0.83", as if you had a 1/6 chance to save.
Thanks for the report - you are correct, this is an error. It appears I accidentally introduced it when I refactored hit/wound rolls to have a variable crit target in order to support 40K 10th edition.
It seems that the saves can't be entirely ignored even when starting from 7+ or when the armour penetration would bring the value to a number strictly superior to 6+. In every case, the formula seems to consider that damage can be saved as if the defender had a 6+ save.
Here's a screenshot (with auto-hit, auto-wound, 7+ save) :
We can see that the expected value after save should still be "1" but it becomes "0.83", as if you had a 1/6 chance to save.