Deep electron levels are a seductive idea as these sound logical and are simple to understand. The real problem is that the electron has two faces, being a small carrier of charge and a very tiny EM-mass structure.
If you just look at the charge nature of the electron, what physicists did do including SM/QED etc.. then you end up where we stay today. (rotten SM)
There is some mathematical justification for deep electron levels but already the classic Hydrogen model fails if you only use the charge nature of the electron!
Why do people want to go on with extrapolating a failed model even further??
So deep electron orbits are nonsensical and can only occur as resonances under kinetic conditions. Also Mills has been captured in the same trap. But he was lucky to find one new deep magnetic bond that looks very similar to a charge bond because this bond is based on a topological charge!
Just the consept of that H deep magnetic paring bond is more of a big deal or paradigm shift than some people think!