There's better arguments out there for bringing Caleb back in the wiki but I might as well address this portion of his "compositeness".
The clones serve more as a supporting justification. It's there to explain that it "could" be one of the reasons why he's every character, not the main reason. Plus, we have cases in fiction where a character fights and kills perfect clones of themselves so brutally killing your clones is nothing new. Hell there's even videos where Caleb fights against himself while both have the same playing field, but one of them still gets killed or injured in the end. Along with this, multiple Caleb's on screen at once that doesn't dispel. But in the end, this whole thing is the reason why he has a
Varies tier.
Also, the whole video didn't seem like a joke to me. The video had a far serious tone compared to 99% of his videos. He seemed really serious about the fact that he was losing ideas so treating it as a "joke" is just missing the point, it should explain a part of the narrative of his universe. Treat the video as if he's an in-universe character uploading videos to his Youtube channel in his fictional universe. And no, the argument that his videos take place in the Real World doesn't work here, especially when in the same video he just casually has a device lying around that can peer into alternate realities anytime he wants.
I guess a similar example would be someone like
Monika who exists in her universe but her Twitter posts translates to our world, which is used as a justification for her High-Godly regen but in this case, it's Caleb uploading videos from his universe to our world.