One reason a lot of veteran players ask who is new is so that we know what KIND of advice to give about boss mechanics, as there are often things that are specific to tanks, healers, and DPS. For instance, for Amdapor Keep, there are specific locations that are best for tanking the first and third bosses. If the tank says that they're the one who is new, I'll point out those spots so that they know where to take the boss. Cutter's Cry is another good example: the healer kites the adds on Myrmidon Princess. Knowing which job in the group is the newbie helps the person giving explanations know what they need to focus on explaining.