Are you sure about this? In my tests floating points are always considered partially ordered, not totally ordered. This page [0] even mentions this in the notes towards the bottom.
[0]: https://en.cppreference.com/w/cpp/utility/compare/partial_or...
[0]: https://en.cppreference.com/w/cpp/utility/compare/partial_or...
Specifically these ordering classes are the result of the spaceship operator and the concept doesn't care whether you have a spaceship operator.