Its no different to saying you should be able to use an eSoS at the same level as a regular SoS. You are wanting to do something outside of what the game is meant to allow, so that you are far more powerful than you should be, while earning XP at a much quicker rate.
"Allows you to switch your active epic destiny at a rest shrine during a quest so you don't have to wait until you can speak with a Fatespinner in a public area."
Where in there does it say you can stay in one ED while levelling another?
If someone has an SS of the actual item which states that you can stay in one ED while levelling another I will stand corrected.
If a large chunk of the playerbase exploits and ends up far more powerful than they should be, then claim the game is now "too easy" then Turbine ends up nerfing to make things harder for them, which then has a far bigger impact on those who werent cheating, and now will struggle even more to keep up.