Agreed. This is possibly a good hypothesis to test, but the effect would be small if there is one. If you can find professional research that it provides some benefit, go ahead. But, i wouldn't trust anecdote from someone's home garden experience. Simply not a proper sample nor consistent enough with all the variables invovled to rule out volatility for what is seen in a small scale with uncontrolled variables.
I'm not trying to shit on your idea. Many others have done it too. If you like it, it certainly won't hurt anything, as long as you maintain same DLI as before. Plants react pretty fast to light. that would probably be somethign you can read into to help.. if leaves 'wake' up in a matter of seconds or minutes in reaction to light, then even less likely this ramp up/ramp down of light would have any effect worthwhile. there may be existing knowledge out there that is not a specific test of this idea but could help either support it or rule it out. What you defnitely shouldn't base this on is "it happens in nature" Lots of less efficient things happen in nature. that's a flip of a coin even if one side is slightly weighted.
If you do do it, one thing i'd stress is to do a rough calculation of how much DLI you are losing by doign this and adjust accordingly... contineu to provide the same DLI as before. This may take slightly more power from the light once it is "full day" light, or maybe just 30mins longer running time to compensate for the energy that was lost due to the slow amping up and down of power at endcaps of day.
Chances are that loss of DLI will have a more profound effect than any potential benefit of this.