Thanks - that will be interesting.
On the face of it, any measurable resistance between the chuck and live parts from which it is meant to be separated by "double or reinforced insulation" is rather a worry. Even at 1000V, one would not expect to be able to measure a resistance between two parts even if separated only by a single layer of very thin/flimsy (hence certainly not 'reinforced') insulation.
For what it's worth, I've just measured 4 Class II power tools picked at random (2 drills, one biscuit jointer and one mitre saw), all well-used and relatively filthy, and in all cases got ">1000 MΩ" at 1000V from the metal chuck (or other metal 'working parts') to both N and L (with and without the tool switched 'on'). I'll therefore be interested to hear what you find.
Kind Regards, John