Wave Fxn "collapse" is always "minimum" necessary ?

[Widdekind]

I recently read, that, when a wave function collapses, to an energy state (say) which is degenerate, having numerous states of the same energy, then the collapse occurs into the subspace spanned by those degenerate energy eigenstates (ie, into a super-position of them?). I got the impression, that it was not into any single degenerate energy state, but into some SP of the group of them. Doesn't this amount to a "partial wave function collapse", like those seen in Renninger Negative Result Experiments ? There seems to be some sense, in which WFC is "as little as possible", collapsing only down into as large a subspace of the original, as can be consistent, with observation / measurements imposed upon the system. Is this (crudely) correct ?