TO-247 case maximum current
The SOA curve on the datasheet implies it's okay:

I share your suspicion, but it's quite possible that Fuji's EIAJ SC-65 package is a bit better than Infineon's similar package. There are a number of TO-247 packages with limits in the 120A-195A range (as well as some with less than 100A, as you know), so it's quite plausible, and Fuji has a lot of background in power electronics.
See, for example, this IR selection guide's notes. Some of their TO-247 packaged products are limited to 90A by the packages, others to 195A.
The JEDEC/EIAJ standards only cover physical dimensions so you can't really assume much between different products let alone different manufacturers.
If your motor draws 80A continuous, the MOSFET will likely explode or at least fail shorted when  you try to start the motor, but you probably know that already. I did a little one-off project where we ended up paralleling two (honest) 300A MOSFETs to get adequate margin.