Disregarding resolving power; pixel density and other optic and sensor qualities; that statement is only correct if the FRAMING is kept the same for the two photos (i.e. if the Camera is moved farther away from the Subject to make the shot with the “crop” Camera).
However it occurs to me that as Terri bought a very long lens and also a tele-extender to use on her 7D MkII, then it is UNlikely that she will be moving farther away from the Subject to get the same framing as if she were using a 5D: in fact I think the opposite is more likely and the purpose of Terri buying this gear was to get as much of the Subject in the frame as possible – or in simple terms to get as ‘close as possible’.
Therefore, it is probably very relevant to explain why that statement is NOT true if the Subject to Camera Distance remains the same for two shots, one taken with a 5D (aka “full frame” camera) and the other taken with a 7D (aka a “crop” camera).
If we have an 600mm Lens (such as Terri has) and add a x1.4 Tele-extender and then use that on a 5D, then if the Subject is 30mtrs away, then the FRAMING at the Plane of Sharp Focus is about 1250mm x 833mm.
Let's assume the camera moves 0.25 degrees during the time of the Shutter Release, thus the blur length any edge of the Subject will be about 131mm (relative to the FRAMING dimensions). 131mm Blur is about 10.5% of the width of the Horizontal Framing.
If we now put that Lens and Tele-extender on a 7D and shoot the same Subject at the same distance of 30 metres, the FRAMING at the Plane of Sharp Focus is about 788mm x 524mm.
If the Camera moves the same 0.25 degrees during the Shutter Release, then the Blur length will still be about 131mm, (relative to the Framing) BUT that blur will now be about 16.6% of the Horizontal Framing and as such more obvious to the Viewer’s Eye.
So it doesn’t matter if the two images are viewed at 100% or whatever, if the Subject to Camera Distance is the same and the camera movement is the same, then the relative blur length will always be greater when using the “crop” camera.
WW