Update time! The heatsink plates arrived yesterday, much earlier than expected. Visual inspection looks good. Doing a side-by-side comparison with the heatsink I have from man of light, they are pretty much indistinguishable from each other. I ran several tests with the plastic plate in place, then replaced it with one of the new ones I just received. I used the stickers I got from man of light because the stickers I ordered have not arrived yet. A light coating of Arctic MX-4 was used.
My flashlight is the Mateminco MT07 (aka Astrolux MF01 Mini) with 5000K SST-20 LEDs. All of these tests were performed with the Shockli black 5500 mAh cell. Temperature calibration has been done. Stepped mode levels and top-of-ramp are stock settings. Thermal limit was set to 60°C. Ambient temperature was around 21°C.
“man of light” original on the left, new ones on the right
These observations pretty much match the OP. You can see that heat shedding and sustained output is much better.