No. There is no mention of marriage at all. The assertion was specific to monogamous relationships.
A monogamous relationship is usually, especially when not arranged, established well before marriage. Divorce rates that hinge on years of marriage and not years of relationship does not provide us with any useful information here.
It is rather straightforward. Some monogamous relationships will establish marriage. Sometimes before the four year mark of the relationship. This means that some relationships that fail in the fourth year will also end up in divorce. The date of marriage does not usually coincide with the date of establishing the relationship, however, and thus marriage data is not useful here.
I'm not sure where you find obsession with arranged marriages? The original comment excluded arranged relationships, presumably because people in arranged relationships maintain a relationship for different reasons than those in voluntary relationships. But if you really want to understand his intent, I'm not sure why you're asking me?
Because you said "especially when not arranged" ... I thought you are part of the obsession.
Arranged marriages have a lower divorce rate but a higher separation rate; suggesting cultural prohibitions against divorce and not a higher success rate. It's odd to keep culling those types of relationships out.
I was protecting against silly nitpickers coming back with "Oh, but in my arranged marriage, my relationship began on the day we were married!" But I guess the nitpickers will find something to nitpick about no matter what.
A monogamous relationship is usually, especially when not arranged, established well before marriage. Divorce rates that hinge on years of marriage and not years of relationship does not provide us with any useful information here.