Thanks for the answer Denny, but I need to be able to work with cinema EF lens, not still lens.
And even considering all of your points, my older Ursa Mini 4.6K EF mount is having 100% accurate focus on all cinema EF lens I have been working with.
Why these Ursa models are different in that regard?
BM rep answered that: "this may be within expected tolerances for the EF mount, and if the customer would like to be able to achieve the focussing distance on a specific lens then you can use shims on the URSA Mini Pro to adjust for this"
OK so he is telling us, that it is technically possible to get the UMP to 100% accuracy. Will see about that
Nevertheless, it would have been great, if a camera that is sold as "EF mount" already has the needed shims pre-installed, so the customer is not buying a camera, that is not "EF mount ready".