Yeah, I found this on Japanese Wikipedia. Grain of salt and all that, but to me I find it a very adequate explanation of why Kabuto's writing ended up so inconsistent and messy. I also find it plausible, though I wonder if bigger Kabuto fans than myself won't.
According to the J-wiki article for Kabuto (I believe), Tendou as a character was conceived by Yonemura and his initial writing partner whose name I can't remember as a parody of Toshiki Inoue himself. Tendou's exaggerated behaviors and arrogance are intended to poke fun at how Inoue came across to the rest of the writing team.
The rest of the rough draft of the series blossomed from that as a satire of how Yonemura and other writers saw Inoue's writing style, particular as exercised in Agito and Faiz. So, the Tendou/Kagami relationship was conceived as just a pisstake of the Shouichi/Hikawa relationship, you had the cooking stuff parodying Agito's cooking stuff, the ZECT satirizing Smart Brain, ZECT troopers and Riotroopers, etc.
Now, this is all happening early in development. Later on in development Yonemura and co. were tasked with making sure the ideas come off as something serious and dramatic, since Kabuto would be an anniversary show and Toei needed something that could support better toy sales than Hibiki did. They didn't change a lot of the basic ideas, mind you, since "like Agito and Faiz sorta" was music to Toei's ears at that time.
Then Toei up and decided that it would be a good idea to add Toshiki Inoue himself to the writing team for their next Inoue-like show. Inoue shows up and can't really make heads or tails of what was going on with Kabuto's characters or plot, particularly Tendou.
Inoue ends up just writing his own versions of the characters that aren't really consistent with Yonemura's. I think this is the origin of most of Kabuto's really severe writing problems-- the show tends to end up going in circles as it goes from writer to writer, because the various writers just aren't on the same page.
