Not sure what is with all the comments/questions about asking about or comparing the frequency response of IEMs to OE headphones like the Stealth/Expanse. Regardless of similar measured response they are not directly comparable as they are interacting with your physiology differently and the two offer appreciably different psychoacoustic experiences, regardless of adherence to Harman.
While it's great that these conform well to the target and perform well for a good price, as far as modern IEM responses go there are probably a dozen or more similar ones out there coming out of China that are quite close to Harman or very easily tuned to it with one or two simple low-q/low amplitude PEQ filters, also with similarly low distortion. Many of these IEMs are all using the same well-performing drivers and should all have similarly low distortion, unless there is something seriously wrong with the product. Most of the flaws/distortion measurements of all of these IEMs align closely with the driver specsheets. So I would not say this product in particular is any sort of marvel.
Crinacle himself also has at least half a dozen or more collab IEMs (some of which have come out recently are controversial because they have barely any meaningful difference over the non-collab versions/other products from the companies he collabs with, some of them even had "dummy" drivers), so why is this the first one Amir has got his hands on to be reviewed? Was Crinacle worried about the others not getting a positive review due to deviation from response or other issues? I can only assume it is because Crinacle is aware of the metrics used for positive review (target compliance), and although there is nothing wrong with a bit of targeted self-marketing I suppose, it's very cherrypicked. So I hope anyone reading this review treats this product as if it were in a vacuum, and not associate it with anything else Crinacle has been involved with.
What would "kill" the Kato for you? Is this already not Harman compliant enough..?