ROOSKIE
Major Contributor
Woops, yes indeed. Google this stuff. There is a fair amount devoted to this around the web.The audioholics article seems only applies to bass.
Here is the Axiom article which is about speaker THD in general.
https://www.axiomaudio.com/blog/distortion/
Here is a site I think may yield results for you
http://www.gedlee.com/Papers/papers.aspx
A power point summary from some of the above site
http://www.gedlee.com/Papers/The Perception of Distortion.pdf
By the way, I am not saying any distortion is good, but that 2nd order (and 3rd for some people) is not a very audible or at least the least bothersome distortion if there is going to be distortion.
These JBL 530 tweeter distortions are very narrow band and low order, I suspect they are not audible but someone would have to create and conduct a test to verify my claim.
Back when I was more into the DIY, many people discussed this on the DIY forums as they were creating speakers and trying to determine the best crossover for tweeters and picking low distortion drivers and whatever else. Generally 2nd and 3rd were considered very non-offensive (especially 2nd). If you hit up a couple DIY builders sites I am sure you can find the conversations. I am sorry I just don't have the exact linkage anymore.
Here is one convo that may help or be interesting.
https://www.diyaudio.com/forums/multi-way/139046-tweeter-distortion-audible.html
another
https://www.diyaudio.com/forums/multi-way/121253-geddes-distortion-perception.html
It is also possible that that distortion is cone break up from the midwoofer not fully suppressed. The tweeter might not be stressed in the R162. (I would much rather have cone break up/ringing than a stressed tweet.)