After two days of web browsing, and re-reading your review, I think I understand why Crinacle tuned the Zero Blue and Zero:Red differently. And judging by ASR and other audiophile forums, the new Red is selling very well. I think I understand, but I've ended up with more questions than answers.
If the Harman IE target is 'shouty' because of (maybe) the number of test subjects and differences in test protocol, I'm puzzled by the high zero-distortion rating it received on ASR. I also can't help wondering how Truthears managed to re-tune the Zero while using what looks like an identical shell. Perhaps the inner cavity has been machined differently, but for a budget IEM I can't see the manufacturer investing in two production lines. Or is it as simple as changing one or two lines of code in the CNC milling machine software?