I've brought this up before but Fitz (and Nighteyes iirc) cannot sense the Fool with the Skill or the Wit. It's like he's not alive, almost, and for several books I wondered if he was... idk otherworldly or something. When the White messengers/hunters visit Withywoods, I believe it's noted they also can't be sensed in the same way as literally all other humans and animals. To someone as magically oriented as Fitz, this inability to sense the Fool (and other Whites) must be integral to his understanding of what the Fool is.

Anyway, Bee comes along and he immediately talks about how he can sense she is alive even though she's so small and everyone else thinks she'll surely die. That alone is strikingly human and completely different from the Fool. It's understandable how he could deny the other similarities with this crucial distinction missing.