I reconfirmed the answer from the Yamato Museum. The answer is as follows.
「現在,常設展示の広工廠のコーナーにて,八九式飛行艇・九一式飛行艇等,同廠で製造された飛行機の模型を展示しております。」
「At the corner of the Hiro Arsenal, which is now on permanent display, we are displaying models of airplanes manufactured at the Hiro Arsenal, such as Type 89 flying boats and Type 91 flying boats.」
Therefore, these exhibition models are extremely valuable official models that have survived destruction, looting, and confiscation of troops due to war.
The span of this model is about 1m (92.2cm?), the length is about 70cm (67.6cm?).
It’s a large model.
I guess smart people managed to protect it. As you point out, the details may differ from the actual airplane.
This model is displayed in a large glass case at an angle where the cockpit instrument panel cannot be seen. Since it is a very valuable model, I will negotiate with Museum to convert it into an exhibition that uses a rotating table so that we can check it from various angles. I think you probably want to check the bottom shape as well.