People just frequently complain when a candidate didn't get 50% of the popular vote in an election. I think it's silly, but it's common. Many people's argument in favor of this initiative is seeing that 50% number. If it doesn't actually produce that reliably, then it's not solving the problem people want solved.

Personally, I don't mind if someone wins with 43% of the popular vote. I don't even mind FPTP much, and yes, I mostly vote third party. But from other people in the state, that 50% number was a concern, and I don't think this addressed that adequately.