The important distinction is what it means for it to "be clear". Unless someone has indicated what their pronouns are, using they/them for everyone is the polite option. But if you're using he/him for strangers just because they're "clearly a cis man", you're now imposing a transphobic bias on those whom you use they/them

The problem here is that they / them is only generic to people who speak English as a first language. In my first language, it's a neopronoun, one that you'll see being used if you know a lot of nonbinary people, but that's a good deal less common than several local neopronouns. And none of these neopronouns are so common that they would come off as gender neutral, all of them will come off as "i'm assuming that person has some heavy gender thing going on". Now, that's something that literally goes for almost everybody i hang out with, but still, none of all the genderdiverse people i know use a gender neutral default pronoun for others, not even the majority that at least sometimes uses neopronouns for themselves, not even the ones that are the most into gender abolition.

It's just not a thing we do around here, firstly because neopronouns are so personal and specific here, secondly because our neutral option is "none / use name". And when we don't know the name, we use neutral descriptors like "that person." And that option works just as well in English, so i seriously encourage making more use of it when we're still in a phase were all of this is in flux.