"Oh! There are magic plants here!" she exclaims, approaching a section of mismatched flora edged with white stones. "I didn't realize there would be. I wonder where the gardener is, I wonder what they do?"
"I'm not especially interested in your job, and even less so since getting it would traditionally involve you dying. I don't think a kingdom would be more responsibility than I can handle, but I do think it would be more than I want. I'd just as soon let you go on being king forever; I don't have any complaints about your approach."
"And Rapunzel you've known for a day and a half longer than we have and already you want to marry her."
"Even princesses don't usually see things that - folktaleish in their lives. It's somewhat peculiar."
"Noticing that. Wondering what all kinds of peculiar you might be and whether I ought to worry about them."
"True. But if I were particularly trying to hide anything from you, I think these conversations would be a lot shorter."
He shrugs. "I could have hidden how I feel about Rapunzel, if I'd wanted to. I don't. I don't particularly want to hide anything."
"She's sweet and funny and she has a hell of a mind. And she's just - herself. I don't think I can explain it any better than that."
In that case - after waiting another moment to make sure - he smiles at both of them and goes off to see about borrowing that plant.
The moss does not have any affordances whatsoever for lying.
Omission, sure, if it's used that way, but not lying.
He really loves her.
She might really be - safe. Maybe she can really trust him as much as she wants to. Maybe nothing bad will happen.
She's not completely... settled about it, but she can't think of an intellectual reason not to be. She's just been burned in the worst way.
But Gothel would've made up an excuse not to use the moss. It wouldn't have been hard, even, the way Rapunzel recoiled from it. Would have been plausible to pretend the same alarm.
And he didn't. And he loves her.