Here is a short tutorial on how you can scale a ProBuilder object in Unity without messing up the actual scale of the object's transform (so it still has the scale (1,1,1) and all the textures are correct after changing its size):

1. Prepare the ProBuilder toolbar and move your scene camera to the object in question.
2. Switch to Vertex Selection in the ProBuilder scene controls.
3. Select the object by clicking on it.
4. In the ProBuilder toolbar, set SetHiddenElementSelection to On.
5. Left-click and drag your cursor to cover the entire object with the selection rectangle. Then release the left mouse button. This selects all vertices, including the occluded vertices.
6. Set ToolTogglePosition (the tool options next to the tools in the upper row) to the mode that you need: center will scale the object from the center in all directions, pivot will scale the object relative to the pivot point. The first option is great when you have a complex shape. The second option is useful when you want the textures to be aligned at the pivot point. (Test both modes with a simple cube to get a better understanding of the modes.)
7. Select the Scale tool in the editor toolbar.
8. Scale the object (/vertex cloud) using the scale tool gizmo.
9. Done. Your object has a new size, but the object transform's scale is still (1,1,1) so all other scale related features work as expected.

The example shown refers to Unity version 2020.3.4f1 and ProBuilder version 4.1.2. The rights to the software shown are owned by Unity Technologies.