har
yeah the guaranteed ATAR threshold is still in place regardless of which preference UQ is, however qtac only gives you one offer per offer round. So what they do is they look at each preference in order and determine whether youre eligible for an offer - if you're eligible for your first preference you will receive that offer, if not they look at your second, and so on. If you put UQ second, there's no chance you will get the offer even if you're eligible for it. Because if you are, that means youre also eligible for QUT (bc lower ATAR), which is your highest preference and thus the one they'll give you the offer to. I hope that makes sense, know it's a little disappointing
edit: and in another scenario you could get around this by conditionally accepting QUT and then reordering prefs to put UQ first for the next offer round, but unfortunately your two courses only participate in the main January offer round, so there's only one chance to get an offer for either