@nik921: I pitched this to our Research and Development Team a few months back, and they let me know that they're planning on introducing a 'Fade In' option for the Eye Comfort Shield, which is likely to be added after Android 12 has been rolled out. As the roll out has already begun, you will hopefully see this some time in the new year. I hope this helps.
@nik921: I've not been made aware of the details of the feature, unfortunately. I'm with you, and hope that it allows users to adjust this to their preference via a Fade-In Duration setting with a selection of timeframes.