Can you please explain the issue?
Sure. In the Dev Diary for Spain:
"We thought that its mission trees did not need a major overhaul, as it was already quite developed in
Golden Century, covering most of the Conquest & Colonization paths required as Spain; therefore, we aimed to redesign its structure, adding a few missions here and there to get some extra flavor, and to rework triggers and rewards, to update them in line with the other Great Powers."
From this I would assume you were adding to the existing missions, not replacing them. This is the start of the Golden Century mission tree for Castille:
This is the very first thing you do as Castille; build to forcelimit and then invade Granada with your perma claims.
Castille's Domination mission tree looks like this:
"Prepare Reconquista" and its rewards (the permaclaims) are nowhere to be found, meaning youd have to slowly fabricate claims on Granada to get started on the mission tree.
Personally, im not a fan of the mission trees in general and think the game has far too many rail-roaded expansion paths because of mission granted perma claims on entire areas at once BUT it seems pretty jarring to have these claims removed.
So I assume this was a mistake or overlooked and not an intentional design decision.
If it was the intention to force the player to have to think for themselves sometimes, im all for it, it just doesnt seem to jive with the rest of the content for other unique mission trees (claims leading to more claims leading into yet more claims etc)