I wouldn’t let that effect your opinion on an iem there is no way anyone can hear that and it can be used as just a marketing gimmick. 20 to 20 is what someone who has all their hearing tends to be at most people especially with age cannot even hear close to 20khz. Maybe 15-16
Yes it’s obviously just an impressive number for the spec sheet. I can hear to about 18.5khz and I’m 27 so all I care about is a well designed driver that actually has extension 20-20khz, Shure 846 for example not a great one.