Donning mask
Glueball is quite correct, you can don the mask very quickly, there is no requirement to remove the headset as the quick don O2 mask is designed to go over the top of the headset and if fitted with integrated smoke goggles, is designed to fit over spectacles.
Removing the headset is not a requirement and IMO is often taught incorrectly by some SFI/TRIs.
The clue here is "quick don".