Wow, that is not an acceptable solution. They need to figure out how to get the system to re-encrypt the volume in the background without user interaction. The steps required are beyond the average user. Especially a premium product from a company people spend the big bucks on for ease of use.
Failing that. Offer same day turnaround on startup drives at the Applestore and authorized service centers, no charge.
I think I smell a class action lawsuit on the horizon.
Luckily, there probably aren't that many units in the wild using APFS and Filevault.
The real question is. How could they mess up this bad? How did all the engineers working on this filesystem miss such an obvious gaping security hole? Apple is supposed to be one of the hardest tech companies to get a job with.