It’s great because it’s open-ended. Was Obi-wan himself a clone? Was he a template for clone forces? Was it a designation given to him by clones, perhaps as a form of endearment? Was it a designation to disguise his prior identity as Ben Kenobi? Was it perhaps his choice of Jedi name once he became a true Jedi much like Darth Vader may have been Anakin’s Jedi name? There’s no knowing which (if any) of these theories is true, and that makes it, like the Clone Wars themselves, a brilliant bit of worldbuilding that ignites the viewer’s imagination.
This is the thing I love most about Star Wars- it leaves a lot of to be imagined. I cannot remember which order I watched the films in when I first did, but one thing I distinctly remember was when watching the original film imagining what the Clone Wars could have been when Obi-Wan mentioned it. Suffice to say my imagination imagined something a lot more gritty and messy than what we got but I digress on that. Absolutely love all the possibilities.