We're all just assuming. Typical duping methods require creation of massive ammounts of lag, taking advantage of that, and using it to duplicate items before the server recognizes what you're trying to do. It makes logical sense - Lag is needed to dupe, so duping causes lag. Also, there was absolutely.No.Lag. after 1.11 came out. It picked up slowly, as MH came back to light, and now, as lag snowballs to its fiercest, we notice things like .o8 valks on ladder, imps, wizzygloves.... It's only guessing, but alot of things point at it pretty hardcore.
At least, this is my speculation.