the keynote of his character is his ability to convince himself that whatever he happens to want is what is best for everyone

I agree with that, which is why I find it hard to read him as an admirable character! Perhaps Leo is just wrong.

Possibly it would have involved defining lesbian as an all-encompassing word including bisexuality?

That's not that unusual! I know some people who identify as lesbian and do not sleep only with women. The term is still used colloquially to mean f/f, e.g. "a lesbian love scene" meaning "a love scene between two women regardless of their individually identified orientations." I am afraid I have come out of this interaction with a serious case of side-eye for Faderman.