For those of you who keep asking the same question, I tried to place a mock reservation at the PH Tokyo using the IBM corporate code, and found the following statement listed under "rate description":

Hyatt Contract - Cr Number Required at Time of Booking - Valid Company Id Required at Check-in

As you can see, PH Tokyo is very strict and I am sure their go-by-the-book agents will ask you to show your company ID when checking in.

On the other hand, HR Tokyo and GH Tokyo do not have the above statement when using IBM code. Most Hyatt in US also don't have the above statement. So, maybe that's why company ID is not checked at other locations.