I’ll be honest, if you say “he’s a cis man unless he says otherwise” you need to stop and rethink what you’re saying.
Because you’re enforcing the idea that cis is the default (and by extension “cis unless proven otherwise”) and that’s gross.
Because I don’t think he ever said he was cis. He said he preferred he/him. There are nonbinary people that use she/he pronouns. She/her is not exclusively for cis and trans women. He/him is not exclusively for cis and trans men.
Let him tell us on his own and stop assuming. It’s really fucking harmful and enforces the gender binary and is shitty to trans and nonbinary people.