CKIII has several "fun" toggles for ahistoric behavior, so I'm not sure if this argument fits. For example: you can flip the default inheritence system to favor women or even make the majority of people homosexual.
I'm guessing it's just more or less something they didn't get around to implementing. Perhaps they wanted to tackle it in a future patch or DLC (I can see this happening if turning this on somehow led to buggy behavior in other areas)
Yeah that's exactly what I'd want for marriage. I'm definitely more inclined to think this is just one of many features they didn't get around to adding rather than an intentional omission.
