I’m not sure this is the right forum for this, but this regression is one of the last things blocking our rails 6 upgrade: Rails 6: `Associations::Preloader` not working when given a scope · Issue #37720 · rails/rails · GitHub
At least I think it’s a regression - apart from one other person who said they had a similar issue, nobody has commented on the issue either way
There’s another discussion on the same topic @ Preload no longer associates record with owner when custom scope is passed · Issue #36638 · rails/rails · GitHub
Would love to get a firm answer either way. If it’s not happening we’ll refactor our code somehow but it would be very nice to keep this functionality.