Attempting to See if Sun’s Heat Affects Grass Growth Next to Added Dirt

For my forth year of trying to isolate the reason I see grass growing taller next to dirt I put down on our lawn I chose to test an idea a neighbor of mine had that the increase grass growth next to the additional dirt was due to the darkness of that added dirt increasing the absorption of the sun’s heat, thus supercharging growth. Due to a bad choice in materials this spring’s experiment was not able to really test that hypothesis.
Years 1-3: • Increased Grass Growth...
Experiment and filming mid April through early May 2023

[@IronDruids]

Maybe part of the explanation is the log and those squares act as mulch. So compared to the soil around it the test spots aren't becoming dry.
Or could that be thanks to being shaded? Some grass I know is better for different amounts of sun. Though I think most do "fine" with full sun. Maybe your grass likes less sun for best growth. Or it could be the grass isn't getting enough sun and is quickly trying to grow longer to reach it.
Sorry if any of my ideas are in earlier videos. It has been a year since I saw those.