From my experience this is incorrect. I sent them my slide and bought the plates I wanted. No one said anything about sending my RMR in.
My RMR plates have (4) posts that locate the RMR. From what I have seen the companies milling the pocket for your exact RMR are doing this because they are not doing any posts.
The time frame is the time frame.
I think they are doing them in batches so they sit and wait until they have the amount of slides they need to work on them.
The "your slide work was completed but the DLC failed our QC inspection" is a line of BS. From the stories I have read online almost everyone gets told this. At what point in time do you find another company to apply the finish?
Either way, I am happy with the finished product. I would definitely send it to them to have done.