Yes. In STAR Voting each ballot ultimately counts as one full vote.
STAR Voting perfectly complies with the legal definition of one-person-one-vote.
The U.S. Supreme Court has declared that equality of voting - one person, one vote - means that the weight and worth of the citizens' votes as nearly as is practicable must be the same. There are a few components to this, so we'll break it down further.
1. Every vote cast must be equally powerful: In STAR Voting all ballot data is counted in both the scoring round and again in the automatic runoff. In the scoring round voters are instructed to give their favorite(s) 5 stars and to show their preference order and level of support for their candidates. All the stars given to each candidate are totaled, and the two highest scoring candidates advance to the automatic runoff.
In the automatic runoff your ballot is your one vote, and your one full vote goes to the finalist you prefer. This ensures that no matter how much or how little you liked the finalists, your vote is just as powerful as everyone else's.
For example: Lets say that none of your favorites made it to the runoff and it comes down to your worst case scenario (zero stars) vs a mediocre candidate (two stars.) Your full vote goes to your two star candidate. This is just like voting in a primary, having your favorites not win, and then voting again in the general election for the finalist you prefer.
Some people get confused and think that in the runoff if you only gave your preferred candidate two stars that your runoff vote would be less powerful than someone who gave their favorite five stars. Rest assured. That's not how it works.
2. Every vote cast must be counted in the deciding round: In STAR Voting all ballots are counted in the deciding round and every ballot carries equal weight in the runoff, regardless of the scores given. The runoff is binary. Your vote goes to the finalist you prefer, and the finalist with the most votes wins - Just like a Top-Two general election.
As long as you have a preference between the finalists, your vote will go to the finalist you preferred. Voters who don't have a preference between the finalists (for example if you gave both finalists three stars,) will still have their scores all counted, and their runoff vote counted as a vote-of-no-preference between the two finalists.
Contrast this with Ranked Choice Voting (RCV,) specifically the Instant Runoff Voting version that is most widely adopted. In RCV, many of the rankings which voters put down on their ballots will never be counted, and many of the ballots will end up not being counted in the deciding round of tabulation. On average over 10% of RCV ballots are "exhausted" meaning they can not be counted in the deciding round, even if these ballots could have made a difference if they had been fully counted. Learn more about the ways that RCV wastes votes here.
3. The system must ensure an equally weighted vote, the legal definition of One-Person-One-Vote, and not mathematically advantage or disadvantage specific factions.
In a 1965 Voting Rights Act ruling on gerrymandering, The U.S. Supreme Court declared that equality of voting - one person, one vote - means that the "weight and worth of the citizens' votes as nearly as is practicable must be the same." This has profound implications on voting methods which suffer from vote-splitting, including Choose-One Plurality, and Ranked Choice Voting.
In a gerrymandered election a faction that had a majority can find themselves unable to win due to gerrymandered districting. The result is that the faction of voters targeted by gerrymandering has votes which are mathematically less powerful than voters on the other side.
This exact same thing can happen in voting methods like Plurality Voting and RCV even if the districting is done fairly. In this case the mechanism putting voters at a disadvantage is vote-splitting, not gerrymandering, but the impact is the same. When vote-splitting occurs, a majority coalition or faction who runs more candidates than the other side risks splitting their factions support. This phenomena is known as the "Spoiler Effect" and it can result in electing a candidate who was opposed by a majority of voters.
The astute reader may have noticed that the Supreme Court gave themselves an out with the "as nearly as is practicable" clause, and at the time of this ruling no voting method in use had ever delivered an equal vote, but that changed in 2020 when Approval Voting was first adopted for municipal elections. Many voting methods including Approval, Ranked Robin, and STAR Voting eliminate vote-splitting by allowing a coalition of voters to show that they would prefer any of the candidates on their side over the opposition. These voting methods ensure that every voter can cast an equally weighted vote as required by One-Person-One-Vote, and as a result these methods produce more accurate, fair and representative outcomes in competitive races with larger fields of candidates.