وَالْإِيمَانُ وَاجِبٌ إِجْمَالًا فِيمَا عُلِمَ إِجْمَالًا، وَتَفْصِيلًا فِيمَا عُلِمَ تَفْصِيلًا
Belief is general where knowledge is general, and detailed where knowledge is detailed.
Affirming everything authentically brought by the Messenger ﷺ is one comprehensive commitment. Learning a particular command or report allows an additional distinct and explicit affirmation of that detail.
This is an increase in the number of specifically understood objects of assent, not necessarily a transformation of the initial assent's essence. One cannot be expected to affirm an unknown detailed formulation as though one had already learned it.