I have B16s, installed by myself.
One of the rears did become a bit 'vocal', but that was after being in use for more than 12 months and me spending a day driving with a fully loaded car at the infamous Napoli cobbled/tiled/treched/potholed avoid-at-all-costs-you've-been-warned roads.
Difficult to say from a sound clip on utube, but nothing nearly as bad as yours though.
The main characteristic of the B16s is that the springs are linear and very stiff.
The bad consequence is that in order to get some compliance over bad roads you have to relax the damping too much.
The good consequence is that the car stays very flat allowing very high lateral acceleration. (I installed an eibach anti-roll bar much later than the coilovers and the difference it made was minimal, if any.)
I would suggest they are taken off and the assembly & installation checked again, possibly by a different mechanic, preferably one that has experience in fitting B14s. They should not sound like this from day 1.
hope this helps,
PS: Damien, I understand why you hated them (I also do for most of the time, but then really love them when the conditions are right). The helper springs are there for reason, to keep the main spring seated when the shock is fully extended. Why did you feel you had to remove yours?