You're conflating so many things it is difficult to know how to respond.
Life + 20 is a completely different class of sentencing than the ones in the Wikipedia list. I don't see a large distinction between re-sentencing or not. The end result should still be 20 years, no? "Life without parole + $X years" is functionally equivalent to a "whole life order" in the UK.
The extremes in the list are of two classes:
1. Mass murderers, serial murders, or others who have gone on large crime sprees. These generally carry life sentences without parole. So, they cannot be indeterminate no matter how many years are tacked on, unless they have a successful appeal of all convictions that result in life sentences.
2. The indeterminate sentences you're talking about. Generally speaking, these are pretty egregious, violent crimes with many victims or the same victim over a long period of time. In many cases, the convicted could have received a life sentence, or one would have been mandated depending on the crime and the state.
But this isn't common by any stretch, except on TV crime dramas. A problem is the giving of life sentences to nonviolent offenders (e.g. California's three strikes law). Also problematic is the stacking of charges to compel plea bargain, which is exacerbated by cumulative sentencing. But "Life + 20" is just, effectively, a life sentence with a different label.