Its both, as the "true" ending of the game is where the fortress grinding seems to hit its apex and where the pressure to use lootboxes to bypass or lessen grinds comes up. Then you can run endless social conquests as part of the post-game. If you play the ranked version of social conquests, you get the most reward, but you can also lose your Orcs. There is also a friendly version with less risk (nothing to lose) and less reward.
This sounds an awful lot like MGSV's post-game, which soured my feelings on the overall product a great deal.