I am going by what the Trumpeter kit looked like next to the Tamiya kit...I do not have dimensions for the Type-90, and did not look them up in the internet. I only noticed that while the trumpeter kit looked like a tamiya copy, it also looked smaller. If your measurements are correct, then it appears it was a optical illusion to me.
The two kits that came out in this release from trumpeter, the Type 90 and the LeClerc, have gotten a lot of bad press, and look to have deserved it when I eyeballed the kits thinking of buying them.
Also, the BMP-1 copy that Trumpeter did IS as awful as has been described, especially in the running gear. And the T-72 with mineroller is a buldable copy of the Tamiya kit, but the turret is just horrible, as is the figure.
Trumpeter used to be pretty much a motorized model company, and would copy other companies kits and add motorization to them. THey also made their own kits to be motorized, the T-55 series in particular. But starting with, I believe the M1A1 series of kits, Trumpeter is becoming more of a serious model company.