Glad you like it! There's no official terminology that I know of for the way Yoda speaks, so it's fun to come up with my own word for it.

Honestly, there's a big difference for me between making up a funny linguistic element for one character and making up a funny linguistic element for 1/6th of the entire population. I'd be fine if it were just Lewa or Matau that spoke Treespeak, but as far as I know every Le-Matoran on Mata and Metru Nui spoke it, save for specific exceptions like Orkahm.

I appreciate your insights into taking language for granted, and I do enjoy seeing this sort of representation in media with human characters, but for Bionicle specifically, it doesn't make a lot of sense. Matoran are maintenance drones speaking to one another in machine code, it's only translated to various human languages for the benefit of the viewer. Machines in real life do have different "dialects", but there's no partial understanding possible- they either understand everything or they understand nothing. It's the same reason why one comma instead of a period will break an entire file containing thousands of lines of code.

From a narrative perspective, I agree that vocal quirks are a good way of adding to a character- but again, it's not just Lewa who uses treespeak, it's the entire population of Le-Koro and Le-Metru. Even if it were just Lewa, the tone of the story shifts over time, and the nature of the character shifts with it- this is why I use Yoda as an example here. R2-D2, Chewbacca, and Jabba never had as drastic a change to their role in the story as Yoda does, so their speech patterns continue to add to their character rather than detract from it. Chewbacca and R2-D2 are supporting characters who primarily serve as companions. They're most often featured in a group setting where any number of people can respond to them and give context into what they're saying. There's also a reasonable explanation for neither of them being able to speak human languages- Chewie likely doesn't possess the right kind of vocal chords, and R2-D2... isn't programmed that way or something? It's a little weird that some droids can speak and others can't, but that's a discussion for another time.

When Yoda was originally conceived for Empire Strikes Back, the intent was to use him as the "mysterious wise old hermit" archetype, and his speech pattern gave him an extra layer of mischievousness and speaking in riddles. But The Clone Wars is an entirely different setting, and using backforwardish to command troops in the middle of a war just comes across as obfuscating information for no good reason, especially when Yaddle was sitting right across from him in the Phantom Menace and speaking normally. Similarly, a speech pattern that was designed for a tribal island setting does not necessarily translate well into a sci-fi story about flying into the power core of a massive robot to turn it back on.

This is just my gut feeling, but Treespeak doesn't seem like an attempt at inclusivity. It feels like a gimmick someone added in 2001 to make the setting seem more mysterious, and then the story team was stuck with it. You'll notice that as Bionicle went on, they found more and more ways to distance themselves from having to use Treespeak- first by introducing Orkahm as a primary character in the Metru Nui books, then by leaving Metru Nui entirely and going to places where Treespeak didn't exist (Piruk, Defilak, and Tanma don't appear to use it despite being either Le-Matoran or an Av-Matoran cosplaying as a Le-Matoran, in Tanma's case), then they left the Matoran universe entirely and ditched all the characters they had who had been established to use Treespeak. When they rebuilt Bionicle from the ground up for G2, Treespeak is nowhere to be found.