This point has been made, but I'll chime in to make it again.
Basically every custom builder I know (which is quite a few) comes up against this dynamic from time to time with clients. There is a common and reasonable (IMO) idea among many clients that the wait time for a custom build is fully spent building the instrument. Most of the time, this is just not the case. Most of the wait time is, in fact, waiting for your 'build slot' to come up in sequence. Once the instrument goes into the actual build process, it often goes quite quickly.
Often, this is why a builder may contact a client fairly late in the wait time, with some fundamental question (i.e. wood choice etc.) - this just means that your slot has come on deck and is about to start getting built.
I understand that this can be jarring for clients sometimes, to be asked "where do we start" months after they think the instrument has begun. However, it's just how it goes with the workflow in a custom shop environment.
I usually go over all the details in advance, but will often revisit them as the build approaches, sometimes several months after the deposit has been placed (and, incidentally, probably spent...deposits generally serve the purpose of keeping the lights on and paying for the parts/finish/etc. for the basses that are ahead of yours in the queue. This is standard practice, maybe even inevitable. However, it's also why most builders are very reluctant to approach the notion of returning a deposit.)
None of this excuses bad communication - I firmly believe that a builder should respond promptly to any client who is on the waiting list. The builder should also initiate contact when delays arise that will lengthen the projected wait. Please note that many builders, including myself, do not *guarantee* a delivery date. Most anyone who has done this for a living knows that such a guarantee would be dangerous, as there are way too many externalities (unpredictable finish chemistry, machine problems, etc.) to make that kind of thing practical.
Most clients are understanding of this reality when it's presented honestly.
However, it's also fair to say that, at least from this builder's perspective, I don't think it's incumbent on the builder to "build a relationship" or maintain regular contact with a client during this initial waiting period, unless it's necessary for the build (i.e. to buy materials in advance, etc.). Please bear in mind that the clients whose guitars are currently in process also need communication, and those clients usually use up the small available time that most single-person shops have available for email/phone contact.
Above all - Jerzy is a well-known and well-established builder with lots of instruments out in the world.
He's got a good track record and a reputation to uphold. If you're willing to wait the time it will take, the bass he delivers will surely be as exceptional as all of the JD's I've seen/played. His long wait, like Fodera's and many others, is a function of the market recognizing the quality of his work (i.e. strong demand), combined with his maintenance of a high standard of craft and personal oversight (i.e. short supply). This is, ultimately, what most custom bass clients are really after, and what they're paying for.
Best of luck!