It’s quite different
Tags lower ground pressure by spreading the load over another axle. This reduces road tax
Extra dolly axle the same on special types.
This is just a fiddle to classify gvw to gtw. As it’s blatantly a fake tag axle I can’t see vosa or French authorities taking a blind eye
You should always level a machine but deliberately twisting the bed is wrong as you’d end up with a lathe that winds work out when using a steady etc
A little tickle of the headstock as last resort ain’t too bad.
Personally I’d write that 2thou off as chuck flex
You use a precision level to scrape longer than the straight edge. You can loose control with a long straight edge
Attached are some pictures from the ‘90s when there was still industry wanting stuff rebuilt