Information and light are disparate. Information transfers with sound and light depending on what the information is. Maybe airflow can also be information. The signals containing information may transfer with the eyes when I believe that consciousness can move information. There are many ways to transfer information. Therefore, we can not simply compare the speed of light and information.
Actually, changes are happening... You have defined these changes in your imagination. But you must have real information about this, but you can have it only with the speed of light. Rather, it should be explained why the slowed down light becomes fast again?
Based on the answer to this last question, I think the change you say is instantaneous also happens at the speed of light.
One problem is why real physical phenomena need to be degraded to information!
There are phenomena faster than the speed of light, but we cannot detect (have INFORMATION) about them with our instruments!
On the other hand, the question is good because it is thought-provoking and helps to awaken new thoughts while we search for the answer.
Well the "established" physics says that light because it is massless cannot accelerate or decelerate in any way. The transition in the interface is INSTANTANEOUS thus timeless, zero time.
You could explain this phenomenon though as another nonlocal quantum effect.
My aim here with this, is to prove that I don't need any proof really to prove that the theory is not physical, incomplete at least and self-conflicting.