Two things can happen with VTM-4 in a turn under power on a slippery surface:
1. If the VTM-4 system guesses on the high side as to how much torque is appropriate to send to the rear wheels under acceleration, you can get some understeer or fishtailing in the same manner as a conventional part-time 4WD system.
2. Due to the fact that there is no conventional left-right differential in the rear drive unit, the rear tire on the inside of the turn might rotate too quickly. If it's not counteracted by the stability control, you can get understeer or fishtailing.
However, these effects on the Ridgeline are usually LESS severe and briefer than in more conventional 4WD systems, as I have experienced them. The only time that VSA hasn't corrected them within less than a second, it's because I had let off the accelerator and managed to break traction on all four wheels or just was adrift enough that there was no power to redistribute. Even so, this was very brief. Either taking it slower (like in a conventional 4WD) or faster (letting VSA brake one side of the truck and allowing power to the other side) is the solution, IF your vehicle doesn't have a mechanical fault.
I recommend finding a slippery corner and experimenting (when there is no traffic) with different levels of engine power, and not balking on the pedal.
If it continues to badly fishtail regardless of power application, take it in for service. You might have a bad wheel speed sensor, or a faulty tire, or suspension.