Yes but it was a flawed referendum and never sought to address the issue of a 2 party state - Would the result have been different had there been a proper option for some form of PR I have no idea but the referendum itself was setup to keep the 2 party state with a heads I win tails you lose question
Tbh I don’t think it mattered what type of voting system it was , it was a Lib Dem proposal and the electorate were in the mood for punishing them for bestowing Tory Austerity on the nation even though the electorate had refused to give them the majority to do so in the first place .