Thanatos hadn't expected the words to come out so easily either, but maybe it was because an earlier miscommunication had jeopardized their relationship. He doesn't want to risk this being the same.

"I haven't. I knew we were still testing things out, and regardless of how I felt, it wouldn't be right to unless... unless you were also of the same opinion."

Zagreus can still decide that this relationship of theirs isn't for him.