[2020] Why would this WW2 Japanese tank have better armor protection than Ferdinand?

A nations most used tank is not really a measure of what they are capable of. Germanys most used tank for example was:

Yet they also made:

As far as the Ho-Ri(s) go, we used as much source data as possible: https://sensha-manual.blogspot.com/2016/11/type5-ho-ri-japanese-ferdinand.html?m=1

There are several sources confirming this tanks existence in some form. WW2 Japanese sources are rare, scares and hard to find.

Ammunition on the other hand is a balancing selection per tank. It has nothing to do with sources, but developer decision.