It depends on how they implement the primary process. It sounds as if they're running one big primary, rather than a primary per party. In that case, there could be 100 people on the primary. Only the top 4 of the primary make it to the general election.

It does sound flawed. For one thing, RCV gives you the opportunity to eliminate primaries and just shove everyone on one ballot. I'm not sure what they think they're accomplishing by breaking it up into two elections. But also, a well-heeled party could run dozens of candidates and influence elections just by sheer information overload. Or, if there's some sort of candidates-per-party limit, again a well-heeled PAC could support several "parties" that are all different in name only - again, pushing legitimate third parties out of the primary.

I'm not an expert here, but it seems as if there are some opportunities for shenanigans; it's both overly complex and yet constrained, and IME this makes them more vulnerable to abuse. I can see why it'd get push-back.