unless Japan increased their time at the gym like their western counterpart, then your statement would have merit.
I think Japan really needs to increase their time at the gym. Koga, Inoue, Ishii, and Kurogo are nowhere near Gabi's explosiveness, considering that these girls are of the same height (180 cm). Even Fe Garay, who stands 179 cm, is more explosive than any >=180 cm Japanese OHs. I've never seen Koga spike at over 87 km/hr. It's usually around 75-83 km/hr. Well, I think it has to do with her preference for precision over power.
In terms of block reach, records say that Kurogo has the highest block reach among these 180 cm girls, but I've never seen the Japanese OHs block with their whole head above the net when they play against terminating OPs with high spike reach. Meanwhile, Gabi blocks with her whole head and underarms above the net when she plays against Egonu, yet she's only 180 cm and has lower block reach than Kurogo. Even Saori at 185 cm had never done that. Do the Japanese deliberately block up to their elbow pads? Or is it because they don't have enough muscle power to do that coz they spend less time at the gym?
I read somewhere a long time ago Suelle Oliveira, Himeji's first ever import, a Brazilian, said they spend so much time in ball training, less time building muscles/gyming. This makes me think that this is probably why the Japanese have the best ball coordination skills, but lack explosiveness especially the middles.