This is valid point indeed. Ultron seems like a lottery ticket, and without any factory codes you never know what you get (also the impressions and reviews are then biased). That's why I recommend to buy it as cheap as possible. What makes Ultron so hyped at the moment is the fact that it's dirt cheap, sounds relatively good and has slightly tamed highs (this is for white label without any factory codes, as compared to my a-frame and imo of course). It seems that many T1 owner here are looking to smoothen those harsh upper mids and treble spikes, which my Ultron manages to achieve in some extent. But like I've been saying this is kind of a double edged sword since my Ultron sounds even too soft at times. Therefore, I can't recommended it for all kind of music styles and headphone systems. At least I personally prefer analytical crisp sound whenever it doesn't get piercing and fatiguing. These things considered Ultron might not suit us all and can indeed lead to "expectation bias" (especially since Ultron can potentially be either a 70's Asian tube or 60's Siemens tube or anything in between).
In this case, it all comes down to the fine tuning and synergy. If we compare tubes only by their own absolute intrinsic properties, Ultron is not the best tube. From my tubes I would rate it below the best (7308 amperex, 6DJ8 amperex, 7DJ8 tele...), but it's wonderful tube in those specific situations. I was looking something for rock and Ultron works for me. I guess my final advice is that you should keep buying those trusted identifiable brands if you want to be sure what you're buying. One good advice is to pay little bit more for one of those best early amperexes and be happy. This would, however, take the best fun out of T1 = tube rolling.