Paul-
I'm sure Mica can chime in on this with a more technical & official answer, but I believe what you're experiencing is more of the wood getting used to being a bass.
What is happening is that the Maple and the Purpleheart are aging (for lack of a better term) at different rates. They have very different densities and moisture content and will settle or dry out or whatever they do differently from each other. It's a normal part of having something built from reasonably young wood.
I've noticed the same thing on all my Alembics. The Purpleheart and Maple seem to have a greater discrepency than the Maple and Ebony. I can even feel a difference between the Quilted Maple, Coco Bolo, and Flame Maple in the body laminates of my Series II. All the Maple has settled faster than the Coco, and the Quilt faster than the Flame.
My 12 year old 20th Anniversary made out of Maple and Purpleheart has less noticeable ridges now than it did 10 years ago. They're still there but just barely because the two woods have caught up with one another.
This is the same concept behind the fret nosing out proud of the edge of the fretboard - the metal frets won't shrink over time, the Ebony will (no matter how careful you are with it).
I hope that I'm on target here. I'm sure someone will correct me if I'm not - but that's what we love about this site.
C-Ya.............wayne