Oh. Oh, mum instincts. Because she's Gwen's mom. Yes, yeah, that, because the other interpretation is weirdly terrifying when it's suddenly offered to him free of charge. No gauntlet to run to earn it. No hesitation on Sally's part. The generosity of it makes him dizzy. Catch, there's a catch, there has to be a catch, except when has there been one with Sally?

There has to be a catch.

"Is- Is Gwen here?"

When in doubt: change the topic, kind of.