I wouldn't say 100%.
For swan boat races, they're just unnecessary because we cheat our asses off thanks to hindsight/laziness of devs to not reroll the races.
For the gacha type event, they're debatable, as the bonus stages actually give less of the 0-stamina stage summoning materials. I think that you're better off farming the regular event stages for this type so you can summon more of the 0-stamina stages for whatever side thing you want (I like equipment upgrade mats), on top of the life crystals.
For card flipping, as much as the bonus stages crush the normal stages with regards to event currency, there's diminishing returns on the utility of said currency. Once you get all of the 'good' stuff (where 'good' is whatever you define as for yourself) thanks to wiki contributors, you're basically done outside of running event stages for the daily quests.