If you try to use scale2d on the blue plane in the attached model, select the centre as the origin in the perspective viewport and enter the first scaling factor, the surface scales immediately in one direction only, without waiting for further input.
If you try to use MoveFace in the perspective viewport to move the end face of the tube facing the plane up to the plane the solid develops unwanted surfaces tending toward the world origin. Note that the tube itself was created by Boolean differencing a smaller diameter right angled solid from a larger, rather than unioning two tubes - don’t know whether that has any relevance.
Hello - Scale2d is a planar operation based on the current CPlane, which in Perspective is at 90 degrees from the plane. Set a CPlane to the surface and it should work fine. Or, Gumball-Scale2d (Window pane gumball icon, with Shift key down)
And, yes, moving faces or edges on trimmed cylinders is just… ugly.