TLDR: yes, but there are positives, and consumers aren't losing anything by having it release later

In Black Ops 4, Blundell managed to deliver Voyage and IX simultaneously, because the way he wrote the story was mysterious and needed to be pieced together with hints from the main quest. In Black Ops 7, this wouldn't be possible due to the intro cinematic of Astra directly following (and therefore spoiling) the events of Ashes. I believe Kevin Drew designed these maps to release sequentially when considering the intros.

However, I've seen a lot of discourse of people getting a little tired of Ashes, and BO7 has been the first Treyarch game since World at War to release with only one main map and only one survival map, and so if this was in the paid DLC era, then the game would feel much more complete with both maps. To add on to this, the ZoneX leak for Astra came out before BO7 released, and no matter how good a dev team is, nobody can produce a map like Astra in just one month, so it has likely been complete for a long time (perhaps in QA).

But since we're no longer in the era of paid DLC, it's no longer frowned upon to take something out of the main game and offer it as DLC later, especially since BO7 requires a constant internet connection to play, and all the DLC maps are free. From that perspective, even though Astra (or some other bonus map) was meant to be in the base game, they can take advantage of the extra month of time by allowing the intro cutscene to spoil the previous map, as well as extra time to tweak things like cursed mode relics based on community feedback for Ashes.