How do you obtain the Choir Of One catalysts in Encore as a Pinnacle Op?

I see some discussion on this from several months ago without any solid answers. Some people got the gun and catalysts on their first try, others played it repeatedly and didn’t get the catalyst, saying it’s bugged.

I got Choir back before Encore was a pinnacle op, but never picked up the catalysts. I’ve since played Encore as a pinnacle op (expert difficulty selected) and didn’t get the catalysts.

Do we know the exact conditions that must be satisfied to obtain the catalysts? Is it random? Do you have to get an A grade? Do you have to select a certain difficulty? Does the evaluated difficulty (shown in the top right of the customization screen) have to hit a certain threshold? Is it just bugged?

Thanks!