TLIK > You listed issues that are of really dubious value
I was only partially serious indeed. But why not? One of the problems in modern world is too many choices that makes it hard to commit, expecting a better something later on. So, why not eliminate possible friction items off the table? We have here otherwise reasonable people not being able to agree on whether Hunter Biden is Joe Biden’s son or not. Could you imagine Hasan and Kalla having this argument?! Even if their positions are both unsupported (or maybe especially then), it is better for them to have the same opinions.
You can also say that same opinions and habits are simanim that their middos and attitudes are similar. For example, do we have many families where spouses disagree on a bitter topic of covid behaviors. There are some but most are closer to each other, I think, than two random people from the same community. This is a novel issue that was not discussed at the shiduch but some commonality leads to similar thinking.