A lens that produces 1:1 (Canon 100mm, Tamron 90mm, not the Canon 50mm which is 1:2) on 35mm format will produce greater apparent magnification on a crop sensor camera. We all know of course that it's cropping rather than magnification that's happening here, the the fact remains that absolute size in mm of the image on the sensor will be different between the EF-S and the EF lens, ergo the degree of magnification is in fact different.
Here's the point of confusion that I was trying to point out. There are TWO magnification steps between the subject and your print: subject to sensor, and sensor to print. The lens makers are just giving the spec for their part which is subject to sensor. 1:1 means subject size equal image size on the sensor and does not depend on sensor size. The 1:1 EF lens and the 1:1 EF-S lens has the SAME magnification. Canon can change the 100mm EF lens to EF-S tomorrow by changing the mount and not the glass and the 1:1 spec, the magnification, would NOT change.
The magnification that is different is going from sensor to print which is NOT spec by the lens maker.