Is the main volume knob supposed to affect the bypassed signal?

I was doing some comparisons between my HX effects and QC into the front of my combo amp and found out that when there are no blocks engaged on the QC the volume knob still affects the signal turning it up and down. I also found that the volume knob on maximum is a significant boost above unity gain.

I am not sure of the logic, but this seems wrong to me. Surely the device should be designed for unity gain when all blocks are bypassed.

I also did some playing around with input/output levels in the i/o panel and this also affected it (not always in the expected ways).

Is this a bug?

No, it’s not a bug. The volume wheel controls all outputs. Not the block levels. But you can read all about it in the manual.