The D5 doesn't need a balance shaft, because on an inline 5 the primary and secondary forces cancel one another out...
https://en.m.wikipedia.org/wiki/Engine_balance
The 4 pot feels great, is very well mounted, superbly sound insulated, and all this will have an impact on the drivers
perception of refinement but the laws of physics simply preclude an inline 4 being
smoother than an inline 5.