My research seems to indicate that along with strengthening the antoninianus, Aurelian also had a massive shift in portraiture style that coincided with the reform. These two coins from @tenbobbit show it best: The pre-reform coin features a bust that looks rather similar to Claudius II and Quintillus, what with the strong jaw and cheekbones. And then all of a sudden, all future Aurelian coins feature an insane giraffe-neck that looks so strange in context. The neck gets even longer, as shown by this one I found on Wildwinds. Why would Aurelian be game with this insane game of neck-stretching? I can't imagine any emperor looking at the giraffe-necked prototype and saying "you know, I think that giraffe is my spirit animal and captures my likeness very well." Here is historical footage of Long Neck Aurelian with his buddy, Wide Neck Licinius
That first coin looks a lot like Quintillus because it is Quintillus. The first part of the legend contains "AVR" - IMP C M AVR CL QVINTILLVS AVG. Your point still holds, though, about the shift in portraiture. Here's an early Rome portrait of Aurelian looking a lot like Claudius II with maybe a hint of Quintillus: And here's a Siscia, along with a near copy of the portrait on a slightly earlier Claudius II: Post-reform with a long neck:
Wow, that's my biggest oops I've had yet on this site. I'm embarrassed.... ON THE BRIGHT SIDE, It's a Quintillus! Yay! Lovely Daddy Long Neck coin you've got there!