Hi Michael,
Thanks

Very clear explanation which will be usefull in future creations.

I think I don't have made a clear question.

It's about this behavior :

when I edit the dimensions of those selected points as you can see it in the screenshots.
I edit the size of the selected points and the consequence is that MoI change the selection from top points to bottom points as if it lose its selection and redo another selection with some other points.

If I do a revolve, this behavior does not appears.