Neo,
As much as I hate to say this, it doesn't sound unusual. And not just from Robart, but from many manufacturers in many "sectors" of our hobby. IMO, as soon as you ask for a "custom" anything, you need to be prepared for just what you're seeing. Robart makes their money by selling "off the shelf" retracts. They do nice work on custom retracts, but (again, imo) it's not where they make their money. Someone with a "big" name might get a better response, but not your every day modeler. Again I want to emphasize, you can substitute a lot of other manufacturers name in place of Robart above. Many are the same. I've had dealings with Robart, and CJM (to name 2 retract manufacturers) where I waited way longer than quoted for my retracts. Last time I talked to Robart about a custom job they would not commit to a date (and so, lost the order).
IMO, if you want custom retracts, go to a custom manufacturer. There are some that make their money from "small" orders. Cost is probably higher, but they will give you an honest answer to the "when" question.
I've seen this same issue from kit manufactures (some that claim "off the shelf"), retracts, custom electronics, etc. It can be very tough these days to find someone who will give honest ship dates (and try to stick to them). This is a hot topic to me
Hope you get them soon, and I hope they meet your expectations.