I think the only difference is the factory setting on the parallex distance in non-adjustable scopes.
"Rimfire" specific are set @ I believe 75 yards vs 100 for "centerfire" scopes, or distances close to those.
I use standard, 1" tube, centerfire scopes on all .22's I have had, never had any issuses with seeing the target.
Airgun scopes are a different story though.
Was this a salesman telling you this?