Marriage paperwork in Japan is proof of relationship required?

Hi, I have a question about marriage procedures in Japan.

I was talking with a foreign colleague when the topic of marriage came up. He married another foreigner here in Japan, and he told me that when they submitted their paperwork, he had to provide proof that they had been together for some time, such as chat screenshots and other evidence of their relationship.

That surprised me, so I asked a Japanese colleague who recently got married. He didn’t go into detail, but he said he basically just did the paperwork and didn’t mention having to show chat history or proof of the relationship.

So now I’m confused.

If two people get married in Japan, do they have to prove they’ve been in a relationship for some time (like showing chat history, photos, etc.)? Or is that only required in certain situations, such as when foreigners are involved?

Why would someone need to submit screenshots as proof?

Thanks in advance.