In fact, itīs the sort of dumb statement that makes you just want to switch off and never come back.
On further thought, it seems to be part and parcel of the crap that digital photography has introduced into the photographic vocabulary; not the semantics but the nonsensical claims of the new snake-oil salesmen.
Has nobody told this gentleman that matter can neither be created nor destroyed?
I'm pretty sure that the OP meant that thee original slides don't hold as much VISUAL data as a 5D, not that a 5D creates data out of thin air. And that happens to fit my own observations. Remember that grain isn't VISUAL data. You probably need 30 or more mega pixels to capture the contour of each grain but that's not to be confused with the info that the grain tried to capture. In reality, none of my Velvia slides had more than 4Mpixels of visual data when I did the following simple test.
Scan at the highest resolution possible on a good scanner (Coolscan 5000 series).
In Photoshop, downsample (Bicubic sharper) the original image to various resolutions (1, 2, 4, 5, 6, 8, 10 MPixels).
Now save each image as TIFF, reload them in PS and upsample them to the original source resolution. Compare with them to each other and look for details in the foliage, sharp lines but not grain detail.