Thank you @Werner it just worked perfectly once disabled. That'll teach me to enable things.
Beyond lower CPU usage compared to a USB to SATA adapter, I have some performance benchmarks.
// write
dd if=/dev/zero of=testfile bs=1M count=3000 oflag=direct
3145728000 bytes (3.1 GB, 2.9 GiB) copied, 11.382 s, 276 MB/s (usb)
3145728000 bytes (3.1 GB, 2.9 GiB) copied, 9.74696 s, 323 MB/s (sata)
// read
dd if=testfile of=/dev/null bs=1M iflag=direct
3145728000 bytes (3.1 GB, 2.9 GiB) copied, 10.8119 s, 291 MB/s (usb)
3145728000 bytes (3.1 GB, 2.9 GiB) copied, 9.09585 s, 346 MB/s (sata)
And some Jellyfin CPU vs Hardware accelerated transcoding usage: