Just think, on the 407 patch you sanded off all the 407, leaving two full coats of epoxy
and doing all your sanding
in relatively easy to sand filler.
On the straight resin patch, you have probably sanded the majority off, leaving very little millage, and doing all your sanding
in rock hard neat resin.
This is why I usually do a double pass with the 407, catching a chemical bond. It gives you enough material to sand fair without removing any of the precious two coats of neat resin.
Your trowel work was not bad, you are just mixing a bit thick. Mix to mayo consistency, or just a bit thinner, so it flows out like paint
. It also provides a superior barrier and is less susceptible to moisture intrusion and failure when mixed this way. But it is a bit harder to sand.