Because, of course, inevitably! it has changed... for stage kinda reasons.
Instead of the upright style of rocker we liked at the warehouse, we're going back to the lower, more rounded Windsor-style rocker the actors have been using in rehearsal. Because it works better with the stage violence.
A Windsor rocking chair from DesignBoom.com
(Where's there's a nice illustrated history of rocking chairs.)
THIS is actually how you choose stage furniture: by looks and design and sturdiness etc., by trying out various options, but most of all by deciding what "plays" best.
It has to play.