They're also leaving almost half the volume in bits on the ground.
Volume of a sphere of diameter 1 = ~0.52 Volume of a cube of 1 unit = 1 Volume of a cylinder = ~0.79
So not only are they not doing the required job. They're wasting twice as much time and material than needed to make the job easier...
And you could still build a pyramid with cylinders...
I have AMD hardware acceleration working for Plex in an LXC container with an AMD APU so I'd assume it's possible.
Tdarr seems to use ffmpeg under the covers, so I'd focus on getting that working with amd. If I remember I had to install the mesa drivers and pass in the /dev/dri folder. Then you can check ffmpeg for the amf encoders (AMD media framework).