It's more important that the bike fit you. So if the gravel bike feels better, then just put what ever tires on it you feel appropriate for the road and be done with it. Once you've ridden it several thousand miles, If you then think you should be doing better than you are at that time maybe it can be figured out what your next bike should be.

Guessing and imagining that we do here will leave you never being able to decide what bike to get.

While the gravel bikes seat tube is a tad slacker on various models, it's not that much slacker.