I searched around and couldn’t find this listed or anything to confirm if it was as designed or previously reported
Fate is rarely fair, 2x damage active:
10/10 Blood Baron does 16 damage I gain 16 life. Looks like is is doubling the original 6/6 and then +4/+4 is only counted once.
I have a screenshot if wanted/needed showing 2X damage mode and a 12/12 Djinn doing 24/24.