I checked our delivered UR5e package against the fixture drawing the seller confirmed, and the tool bracket arrangement plus label suffix differ; the seller says equivalent without a dimensioned comparison, so our tooling remains unfitted while I ask what exactly has changed.
Send the agreed drawing revision and delivered identifiers together, then ask for a marked comparison of the interface dimensions and any effect on your tool position
They confirmed drawing C before purchase; the delivered bracket is marked E, and its shoulder sits farther forward in the external comparison, though I have not treated a photograph as a dimensional measurement.
Get the delivered identifiers into the equipment folder once this is settled, because my tidy tray notes became confusing the minute a physically different spare turned up under the same description.
I would ask them to price supplying C as well. You might decide E is usable, but all the review time for their substitution should not become your default project plan.
David's alternative is worth having; an equivalence discussion can otherwise keep going simply because nobody has asked how hard it would be to deliver what was agreed.