The two are separate because the re-definition of "marriage" required to include same-sex couples means that "marriage" no longer can imply sexual or erotic relations of any sort. This because there is no way to come up with a conception of marital consummation that will apply equally to same- and opposite-sex couples. Defining consummation as coitus is heterosexist bigotry. Defining consummation as any act of penetration excludes gay men who prefer frottage and Lesbians who eschew strap-ons and fisting, and if you define sex as anything that could lead to orgasm, given the infinite number of fetishes, anything could constitute "marital consummation" ranging from walking around barefoot to wearing a bathing cap to crying.
The individual fetish thus determines "marital consummation", thereby making it too subjective for a legal definition. Thus, "marriage" laws must jettison the legal concept of "marital consummation" altogether and therewith the notion that "marriage", be it same-sex or opposite-sex, has anything to do with sexuality.
"Marriage" now is nothing but a way to file joint tax returns and share pensions.