...which is one of my major (of many) complaints about all "scaled agile" frameworks: the promise is that you put all this planning effort in we won't blow up your plan for the next 4/6/n sprints; you get stability and predictability, and can actually shave a yak or boil the ocean, things that are hard to progress with just a 2 week window. Who has ever seen an org with the discipline to NOT do this? Executives are rewarded for the "action imperative" and quick course corrections. They want big, bankable delivery dates AND agile responsiveness to fundamental goal changes. Good luck.