Qt styles and colours

In the past, only haiku widget style was using haiku colour scheme, the other Qt widget styles were imposing their own.
Users that have modified their haiku colour scheme were able to use one of these other styles to ensure that everything would work with their Qt apps. It was useful in case that you messed up.
But with latest Qt releases, this safety net has disappeared and all Qt widget styles are adopting haiku colour scheme.
If I understand well Windows and Fusion widget styles are provided with Qt; Cleanlooks, Motif, Plastique and CDE widget styles are provided by qtstyleplugins. Anyway all are affected by that change.
Is it a “normal” evolution or is it a regression in Qt?

Since version 5.15 palette mapping have been moved from styles to qpa (platform plugin). This change applies to all systems - not just Haiku.

Thanks for the clarification.
Sad, it was handy.
Then, would it be possible to add an option in the Qtconfigurator to make Qt apps to use Haiku default colour scheme instead of the current one so people would still have a fallback if needed?
A similar solution could be used also for non-Qt apps using old layout api like Beam.