I'm not sure how the Japan Meteorological Agency defines sustained vs gusting winds, but I believe it's forecast to peak in intensity today with the following:
Central pressure
915 hPa
Maximum wind speed near center
55 m/s (110 kt)
Maximum wind gust speed
80 m/s (155 kt)
I don't think that would quite be Cat 5 but their measurements might be different too, I'm not really sure.
Here's how the Japanese government is talking about it (with help from Google Translate):
The Meteorological Agency and the Ministry of Land, Infrastructure, Transport and Tourism held a joint press conference one after another on the 3rd and 4th, calling for the maximum caution against the approaching typhoon No. 10 using the word "special warning level". The "special alert" is one of the largest alerts that indicates an "emergency situation", such as once every several decades. It is unusual to mention from an early stage that the forecast may change depending on the future course of the typhoon. In order not to cause a serious life-threatening situation. If there is an unprecedented danger, it is necessary to be fully prepared and vigilant.