It's okay by me
With one twice divorced daughter and one once divorced, I have no illusions about the purpose or sanctity of marriage. My own bond with my pal of 40 years has nothing to do with any marraige vows.
From the standpoint of pure tradition (I like tradition) I would favor the term legal union as an option for same sex couples as well as heterosexual but I would not walk to the curb to object to whatever they want to do, including dispensing with marraige and calling both legal union.