Without an EMS in the mix our Honda 3000i ran for years with the ground/neutral un-bonded.
Then we added a Progressive Industries EMS-HW30C to the mix and it showed an error of "Open Ground" when on the Honda. A call to PI's Tech Support (Outstanding BTW) lead me to purchase a replacement male 15 amp extension cord plug which I wired to bond the Neutral to the Ground. The Generator is bonded to the trailer frame as well but they indicated that was not a requirement. Now the EMS is happy and I can monitor the incoming volts & current etc. so I am happy.
I'll probably lift the generator to trailer frame bonding in the near future.