Hi Black Mammoth,
If your impressions/divots are springing back and aren’t visible when you aren’t on the mattress then they wouldn’t be body impressions which are visible and can be measured with a straight edge or string across the mattress surface when there is nobody on the mattress.
The top layers in your mattress are fairly thick and soft so it sounds more like they are doing what they are supposed to be doing and compressing when you are on the mattress and then coming back when you aren’t.
They now have a new version (5th generation) which they recently introduced which replaced the 1.5 lb polyfoam in the top layers with 2.5 lb polyfoam and with this change there wouldn’t be an obvious “weak link” in the mattress (see post #19 here). I’m not sure exactly when they made the change or which one you may have.
Phoenix