I thought I had seen that happen when watching streamers but always when I was paying only limited attention. Thanks for posting confirmation.
In my opinion, this would be the bug. The 9/9 with +1/+1 should summon an 8/8 upon dying.
Of course it’s different. But all cards that retain buffs and debuffs retain damage as well. All cards and effects (other than “silence” and “healing”) that reset health reset buffs and debuffs reset as well.
You’ve made your point. You believe this is either incorrect or confusingly worded. The QA department has seen it or will see it, and do what they think needs to be done.
Since this is the bug report forum, not a discussion forum, I’ll not respond further, except for one thing:
Have you any screenshots or video you can share? I have not seen any game yet with a Rattlgore / Undatakah interaction and I’d be very interested.