I'm only posting to prove a point because IMO plants just grow in the schedule you give them....
Anecdotal evidence may have practical value but it does not prove anything. Proof by giving examples is not valid.
The fact that plants grow on the schedule that is provided does not necessarily negate the existence of an internal clock. E.g. flowering activities in some plants may be governed by an internal clock.
Observations on a limited set of plants may not apply to all plants.
More study has been made of plants with agricultural applications than have been done with the plants we grow. It is my understanding that the cyclical nature of plants is not fully understood.
My own observations agree with those already stated. Shifting the time that the lights are on does not appear to adversely affect plant growth.
It often rains in the middle of the day in the tropics. So, turning lights off a few hours in the middle of the day would not seem to be that unnatural.