(Ignoring that it was all retconning) I think force sensitivity wouldn’t necessarily be an indicator of anything. Force users can probably detect some amount of force sensitivity from others, in varying amounts. Most people are probably weak, with a few standouts here and there. But latent force sensitivity probably doesn’t set off any alarm bells the way a “trained” force sensitive would. So if he had detected she had any training, like I assume force users somehow “guard” themselves against others probing, that would’ve set him off and he’d realize, she’s hiding something. Also, given that this occurs literally right after the events in Rogue One, he was probably more focused on retrieving the Death Star plans.

Luke would’ve had a stronger connection to Leia than Vader would’ve, given that they’re twins, so he would’ve felt a stronger pull than Vader. Vader is the kind of Dad that probably would’ve forgotten his kid’s birthdays and social security numbers.