SRV-PR (the method that is most commonly brought up when disusing the proportional multi-winner version of STAR voting) is not even proportional. If you want further proof of this, check out the example Warren created where it can fail to elect a Democrat when 49% of voters give a max score to the Democrat and min stars to the Republicans: https://groups.google.com/forum/#!searchin/electionscience/proportional$20srv$3F%7Csort:date/electionscience/aOMyxkoey4Q/KepDTrY7AwAJ (the example is mentioned in Warren's first comment in the linked discussion). It can meet relaxed definitions of proportionality in which each party runs clone candidates equal to the number of seats up for grabs, however the only reason these relaxed definitions of proportionality work is because they rely on candidate cloning which is something that turns SRV-PR into RRV just like it turns STAR into score.

Obviously STAR voting advocates shouldn't advocate for a broken "proportional" voting method that isn't even proportional. But they still need a proportional multi-winner version of STAR voting method that they can mention to as a long term goal when ever the topic of proportionality comes up.

Here is a discussion about what that method should be: https://groups.google.com/forum/#!topic/electionscience/HkgoqQiGN4k