Hello @Tom_Russell,
The reason why you are seeing an enhanced Signal Path is because you are applying Crossfade to that zone.
For Roon to process crossfade and other DSP operations, the bit-depth is often converted to a highly-precise 64bit float so that the calculations for that operation can be performed. You can read a bit more about this here and here and to turn it back into lossless all you would need to do is disable Crossfade. Hope this helps.
Thanks,
Noris