[x] Big career retrospectives

... as examples we have Decade by Neil Young, Beckology by Jeff Beck, and the Robert Plant one whose name I can't remember.

While a lot of the work is solo, there are usually tracks on there by bands in which the person participated (in Young's case there's Buffalo Springfield, CSNY, Stills-Young Band and of course several incarnations of Crazy Horse).

Now: the quick and dirty interpretation about how to document such entities is as (for example) "Decade" by "Neil Young" and mark it as a "Single band compilation". The tracks which are by the various participatory bands would then be marked as (for example again) "Crosby Stills Nash & Young": "Decade(released by Neil Young)" and still set as a "Single band compilation".

Would this still apply if the band isn't actually credited as being that band? IIRC, "Helpless" (for example) was not credited to CSNY on Decade - so would they be actually indicated as having such an entry above?

No, they would not. If they are not properly attributed to the recording band, then we consider them orphan tracks that we do not document.