Does completing "Establish a Temple to Ibrundul" count as taking Piety quests?
I haven't been able to find an official answer for you but I would say that yes, you're interpreting it correctly. The wording in Lords of Waterdeep is usually quite clear and the keyword is the same on both cards. Due to the first card you get a cube each time you take a Piety quest and the second card instructs you to take a number of quest cards. This means that you will get a cube per Piety quest taken.