Mark - because the reasons are that Kano had this kid at 16 and in his personal diary described him as an ordinary (but dedicated) kid. Furthermore, because he actually is not known to have spent much time with Tanomo at all: the adoption being a post-war adoption of an orphan to give him a name. Because there was no contemporary accounts whatsoever of Saigo possessing any kind of IT. What he was described as being was a phenomenon cat-like athlete, like this guy
. Because the first accounts that suggested that Saigo had something from Tanomo came AFTER Ueshiba was getting well-known (and as Shishida's research shows, was opening teaching "how to beat judo" AND after his teacher, Takeda Sokaku, who was alleged as having studied from Tanomo, was also getting prominence.
Couple this with the fact that both Sagawa and Sato Keisuke (the one his leading student in terms of skill, so say many and the other, the most disinterested, no ax to grind whatsoever guy in the bunch, both assert confidently that Tanomo almost surely didn't teach Takeda.
1. Kano had a private school, teaching young men how to live and how to do judo. Among his teenage students was Saigo Shiro, somebody he described in private writings as, at that time, being easily tired, and that they couldn't practice together long. (In other words, we aren't talking about Kano recruiting a "sandbagger" to enter into tournaments. He was just a kid who associated with him before all these alleged tournaments.
2. He became a brilliant athlete, and with a lot of top competition in the dojo, flowered. His most remarkable quality, by contemporary reports were two things: he took ukemi like a cat. He could twist in mid-air and land on his front, which, if you are keeping score by back fall, as they did in jujutsu tournaments, is a good trait. Secondly, he is described as having prehensile toes - HIS yama-arashi was enhanced, so it was said, by him actually gripping the other guy's ankle with his toes. There is NOTHING, even in the many decade later accounts that describes IT.
3. Because long after he'd left the Kodokan - and after he'd died, so he couldn't refute anything - and after Ueshiba and Takeda were achieving increasing prominence, then
the story arose.
4. Because two of Takeda's top non-familial disciples expressed doubt that Tanomo knew anything about martial arts. And because the historical record supports this. (notwithstanding my little caveat at the end of HIPS that there is a faint possibility that the family, as a whole, might have had the remnants of a martial art transmitted from China).
5. Given that there is good evidence to suggest that there was a jujutsu school in Aizu that had some kind of internal training, a ryu that his maternal grandfather was a master; given that his father very likely studied jujutsu from that grandfather, his father-in-law, as we know he studied spear and other arts from him; and given that Takeda, by report, manifested IT as a young teen, before he would have met Tanomo,it seems to me the really wonderful research would be to get to the Aizu area and find more records regarding that school.
8. Back to HIPS. My first chapter established that Chinese information was widely disseminated, what widely regarded, and widely accepted as a primary influence on Japanese martial arts. It's just that this hasn't been written about in English. There's nothing hidden about that. Japanese schools didn't hide it - witness Yoshin-ryu, witness Kito-ryu.
9. Finally, regarding katakana. I have a student notebook of the Araki-ryu, written in 1858. In successive sentences, the writer would use a kanji, then the same word in katakana, then a mixture of kanji and katakana, and then back to kanji. Didn't mean anything. Just taking notes.