In D&D XP is a meta-currency that is tied to advancement - Gain enough XP and you gain another level of class abilities, HP, saves, skill points, etc. The GM is using it to encourage a specific style of play. That is one of the best uses of XP in any system. If Florian wants to encourage dungeon-delving adventures, he should be giving XP for interacting with the dungeons. The players are free to accomplish the greater goal without interacting with the dungeon if they so-desire. In that case, they are rewarded with whatever was promised at the on-set of the quest.
The only time this would be inappropriate is if Florian said, "This quest is worth 10,000 XP" and then when the players finished, if they didn't go through the dungeon, he said, "I'm only going to give you 5,000 since you didn't do my dungeon."