You would think so but it can be that obvious and a weak-willed woman or one that's extra lonely that week will go "aww, forreal?". And he might not say it after she says that. If he's truly good at his game, he will slowly build up to it.
Which honestly he should've been doing in the first place. When trying to secure someone of the female gender, all you have to do is treat her like she's the only goddamn thing you see while at the same time not really showing her any affection at all. That way you can claim that you were just having fun outchea when she inevitably starts catching feelings.
Women are different but in my experience all tend to think along the same lines. Once you figure most of it out, it's not really that hard to get them to give it up when they promised themselves they'd wait.