All ammo manufacturers have tiers of ammunition with higher quality components and quality control being used as you go up in price.
Most of the Rio ammo I've seen has been their lowest tier ammunition because people buy the bulk stuff to use in classes. Even so, their bulk stuff compared to other manufacturers bulk stuff is another level down in quality. I would happily take Federal or Winchester's bulk birdshot ammo lines any day over Rio. When I buy bulk birdshot it's usually Federal Top Gun or Winchester Super Target and both have been worlds better. Same goes for experiences with other bulk buckshot and slugs.
I'm not comparing Rio's cheapest stuff to Federal Flight Control. Bulk ammo to bulk ammo, Rio is the worst out of the bunch. Remington hasn't been a whole lot better in recent years. Federal, Winchester, Fiocchi, and S&B tend to be better bets.