In the context of political parties, where a voter can only affiliate with one party and vote for one party, it's fairly easy to define proportional as you say, @wolftune, that "if there's a clear block of voters enough to have a quota of a seat, that block gets to elect whoever they prefer."
This is a simple and transparent result, which has value, but it's not necessarily the best result, because we know that voters are not factional hardliners that agree with their parties only and disagree with everyone else 100% all the time.
For a better example we can take 6 parties with candidates; Red, Orange, Yellow, Green, Blue, Purple. Blue voters would give Blue 5 stars, but also like cool colors in general. Orange voters love Orange but also like warm colors like Yellow and Red. Red voters also like Orange but also like Purple. These parties supporters also tend to like Brown, though it's not a color on the color wheel and thus not a real party in Colorland. Lets also say that Red and Purple voters actually slightly prefer Ultraviolet and Infrared, though those colors make no sense to most voters.
In a quota rule PR election where there are 6 winners is it fair if Brown, who is liked by all and highest scoring overall never wins? When parties overlap and Venn Diagram, who is to say which is the "real" faction? Is a winner set the most representative if Ultraviolet and Infrared win, even though they were disliked by every other faction, while Red and Purple were also loved by their supporters but were also well liked by their peers?
My point is that real voters have nuanced preferences, so an expressive 5 star PR method can and should take the strength of those preferences into account. (Allocated Score does this in determining which voters get allocated to a given winner. Adding runoffs to the winner selection, or doing Monroe Selection would do this even more, with some added complexity.)
As said above, the definition of PR that we use for List PR or STV, if applied to a score ballot, would say that if a quota bullet votes then they will win a seat. That works for ordinal methods, but it specifically selects for polarizing winner sets and could care less about electing candidates who represent more voters when possible. This also might allocate voters and consider them represented by a candidate who they ranked 5th and dislike, or who they only voted for as a lesser evil.
We could also aim for a stricter proportionality criteria that does recognize and reward consensus candidates, particularly if they are alternatives that are representative for factions that slightly prefer a highly polarizing or antagonistic option.
A reasonable definition of high spectrum PR might be that "if there's a clear block of voters enough to have a quota of a seat, that block gets to elect the most widely supported of the candidates they like." Another way to think about that is that "that block gets to elect the least polarizing of the candidates they like." (Q: what score is a candidate who is "liked" by a voter? 4? 3?)
This guarantees the most representative proportional winner set possible and likely would find the most effective but still diverse winner set. It doesn't guarantee that everyone gets their favorite. It does get each faction an advocate who is likely to be more effective with the larger elected body, however.