Why does Fatwa No. 48551, regarding "Is one excused for insulting the religion out of anger or ignorance?" contradict what came from the early scholars such as Ibn Taymiyyah, Ibn Uthaymeen, and Al-Albani, concerning absolute takfir (declaring someone an apostate) and takfir of a specific individual?

What you have mentioned regarding the distinction between a general ruling and a ruling on a specific individual, and between a ruling on an act and the doer in matters of disbelief (kufr) and transgression (fusuq), is the relied-upon view. Matters known by necessity to be part of the religion, such as associating partners with Allah in worship, mocking religion, and reviling it, do not admit an excuse of ignorance. An excuse of coercion for reviling religion is accepted if the heart is firm in faith. Abandoning the hijab (definition) is not an act of disbelief that expels one from the fold of Islam. As for abandoning prayer and ruling by other than what Allah has revealed, there is a difference of opinion and detailed discussion.