Yes you do have to, but I developed a technique to make it pretty easy. The flair videos have you using a bowl of some sort as a water container and submerging

Yes you do have to, but I developed a technique to make it pretty easy. The flair videos have you using a bowl of some sort as a water container and submerging the chamber entirely, whereas I just place the brew chamber on a piece of granite. The lapping of each is sufficient to form a watertight seal, and I use the minimum amount of water possible, which is nice because waiting for the boil is the longest component of my process. All in all the preheat probably adds <1:00 between time spent actually preheating and the additional time it takes to boil the extra water needed for preheating. That said I do prefer more acidity in my brews, so I only opt for a single flush of preheating water. Some people do 2 or even more, which would obviously take more time.