Well, this is all very interesting.
Because if you look at Anderson’s Dictionary of Law circa 1906 you will see how he defines “marriage”.
It is totally common law and has nothing to do with statutes at all.
Some of his requirements:
Taking each others name
cohabiting as man and wife
purchasing property in both names
announcement of intent or actual ceremony
and there are a few others.
I am not disagreeing with you, in fact this points out what the supreme court is trying to avoid - by making it the same for all jurisdictions.
But in ALL cases, it is one man and one woman...