Meggering Three Phase Motor (Phase-GND, Phase-Neutral, GND-Neutral)
If you follow your own logic through you'll have the answer.

Since your phase to neutral resistance is close to zero then you can consider the phase and neutral as joined together (for the purpose of this exercise).

Now if phase-GND is high resistance then netural-GND must be high too.

This is correct. There should be no connection between the windings and the machine frame.

For the benefit of the unexperienced reading this post, all these measurements are carried out with the motor disconnected from the supply.