The dash is an old school design, which assumes that the pilot might one day need to do something in an emergency that no one could imagine at the design stage.
Indeed, putting the power levers into the ground beta range and below in flight would cause a fair amount of paper work. But so would hitting the back stop of the elevator in a Vne dive....and there's nothing stopping you doing that either! The dash is no airbus!
Not a dash, but clear to all rev is possible before main wheel touchdown.
Photos: Ilyushin Il-62M Aircraft Pictures | !!!!!!!!!!!!!!
Interestly, our ops manual for the dash did not allow to move the power levers below the flight detent before NOSE wheel (ie all wheels on the ground) due to control "issues"
There was a Fokker 50 on the IOM which tried it a while ago, selected rev just before touch down, the loss of airflow over the tail caused it to leave the Tarmac, there's an AAIB report about it somewhere. But another example that it is possible to do what ever you want with the older ac.