I agree with @PyongyangKipperbang . It’s a fake wedding to keep his Gf happy but not risk any of his cash by legally marrying her.
Shes not objecting yet because she doesn’t know it’s fake. She’s expecting a full
legal marriage and he won’t tell her that’s not happening until a few days before. He will then say that his bitch of an ex won’t “ sign the paperwork, she’s doing it to spite us and spoil your day because she’s a hateful person “.
Distraught OW / Mug will say that it’s too late to cancel everything, so he will helpfully suggest just a commitment service / whatever and they will do it legally when his divorce comes through.
They will no doubt already have a humanist celebrant lined up to do this and not a registrar / minister of religion as they conduct legal marriages. Minsters often do blessings but they need to see the legal paperwork first, they won’t do a fake weddings to fool everyone.
They will explain their problem to the celebrant who will Happily do a non religious commitment and they can say their own vows. It will look a lot like a marriage to anyone who isn’t listening carefully.
Then he will keep procrastinating on a legal marriage and she will be scared to complain / threaten / leave because it will be constantly about to happen next month .
Just like all the women on here who move in with a man, have three kids with him and give up work to care for them while “ waiting for a proposal “ which is always going to happen at the perfect time because “ he’s such a old fashioned romantic and wants to do it properly “.