Not sure if this is a user error or a bug or maybe a designed functionality

We are not using the default "Provider", "Hygienist" for each operatory (Setup -> operatories) because of some other logistical issues in the office.
The office staff decides on which doctor / hygeinist will work on a patient based on the appointments and schedule them on certain operatories. We indicate that the color on the appointment should indicate the hygeinist. Now the Problem is that when we move the appointment from one operatory to another, The settings of "Hygeinist" are "Use Hygiene" color for the appointment are lost.
Not sure why the above happens even when I am not using the default operatory settings ?
Any help / clarification would be helpful.
Cheers,
OpenSource