This is where your argument flaws apart. They already delay Savage. Only the subsequent two tiers are released alongside Normal mode.
They delay savage 33% of the time, for reasons that dont exist for the other 2/3'ds of tiers. Theyve said exactly why they release savage late initially, and it doesnt actually make sense there, either.

There is not 10 levels of grinding and 6 zones of content required in order to unlock subsequent raid tiers. The only quests required is the breadcrumb quest that gets you back into the raid area (for Omega and Eden) or to a new NPC in Hinterlands (for Alexander) and the quest given to unlock savage once you do normal. Subsequent raid tiers do not require more MSQ completion nor gear grinding.