Not to mention we've seen him not breathing before. There was also the mention of how he's in a dimension where our laws don't apply. It read as very tongue-in-cheek and is the sort of thing I know I say to my husband when I'm trying not to lie but also not spoil something. Especially with how clear he was with other deaths that were asked about. He also straight told us he couldn't explain why Zenos became a reaper. I have multiple theories on how they could do things, but we'll have to wait and see.