If the Salafi Ulema can give reference for every one of their verdicts then it only follows that the ulema of other schools start giving their evidences. And in this digital age with scanned copies of all books it is very easy to do. You can’t be labelled an Alim unless you know your evidences. The only person who would hide evidences is one who knows they are to weak to present or has no clue about them. Even in darse Nizami when they teach you there are references in some books like Hidayah. Best the students memorize these if they want to call themselves scholars.