Well, assuming that Ueshiba simply used the phrase because it was ubiquitous in the culture at the time doesn't mean that it's just "that tired old Japanese fascination with trees". After all, the ubiquitous term had nothing to do with trees. Sho-Chiku-Bai were used to illustrate grades and levels. For example, produce and poultry would be marked with one of the three, Sho indicating highest quality, and Bai indicating lower quality, much as we use "Grade A" today. In prewar schools, Sho-Chiku-Bai was used to mark assignments much like we use "A, B, C".

In that it was fairly common, particularly in Ueshiba's day, it doesn't seem strange to me that after taking three particular kata that he felt resembled his ideas of , he might then give them the name of Sho-Chiku-Bai, a common term of his day that allowed him to give them separate names, and yet group them together as a related whole. And just as "Sho-Chiku-Bai" would mean something slightly different from the market from the school from the rakugo stage, so it would have it's own particular meaning in Ueshiba's dojo.