If this was Natasha, Sam would think nothing of the offer. He'd immediately assume it was - mostly - continuing the part, following the logical conclusion of using kissing as a diversion to get them an excuse to get out of here and discuss what they'd found. He'd have said hell yeah without a hesitation.

This isn't Natasha. This is Shepard, and so - so he thinks something of the offer.

And then he says, "Hell yeah," without hesitation, anyway, because it doesn't actually matter which way she's asking him.

His response'd be the same.