You are correct. I mistakenly conflated impeccability with sinlessness for Adam and Eve. They were created sinless but fully able to sin. As you correctly replied to me.
Where I was going with this, trying to say before I got it all backwards, was that sinlessness does not define deity. I think some believe it does. Impeccability doesn't even define deity. A rock is impeccable. So is a turtle. Maybe even a dog. The human nature of Jesus was temptable, and presumably capable of sin. The nature was there, a fully human nature just like Adam and Eve were created with. Not a fallen nature yet a true human nature. But the person, not the nature but the person, was impeccable. That because the person was the Eternal Son of the Father, his true identity in his two natures.
It is an attribute just like omniscience and omnipotence, important but not the actual identity. I think we more or less agree.