No, it is not normal to state what percent-better-person you would leave your romantic partner for. It’s cynical and narcissistic.
What if your partner is in an accident that changes how they look or live? Now that they’re X% “less” than what you signed on for, you can just dip?
Like I get being upfront about stuff, but this is just transactional. It’s not about your commitment to another person, it’s about maximizing your return on investment.