The wah block generates NO distortion with the drive at zero. I don't know how many times more I have to say this for it to sink in but I'll keep repeating it until it does I guess. If you are hearing distortion it isn't the wah block.
OK.
Just to put my part in this to a rest....
You're right.
I made some incorrect assumptions about my clean amp tone settings.
Evidently they're not as hyper-clean as I thought.
All the distortion I'm hearing when using the Wah is being generated in the Amp Block.
I proved this to myself by Bypassing the Amp Block and then the Wah is real clean (unless its Drive control is maxxed and then it's a bit distorted).
Move on folks.
Nothing to see here...