otherwise it would be easy to true the wheel on the piss to one side.
Well, that’d be where a dishing tool (or home-made equivalent) came in, rather than using the stand, which I find unsatisfactory.
If the calipers touched both rims on a front wheel (say) then great, but put a rear in and with the different width hub you’d not have that situation again surely? I just true on one side of the rim, flip it round if it really calls for it.
Just to check, you do have the one without the dials don’t you? Not that that would make much difference to the above be honest. You can loosen the two hex bolts holding the caliper to the white bar BTW, if you really want to move it about.
IANAE anyway, I am sure one will be along shortly 😉