Good luck finding an actual list of audio accessories that also support the codec. LHDC's website doesn't even include Pixel Buds; it appears to be a "select" list, so phone support sounds great until considering the need for compatibility on both ends.
I'm not against free upgrades, by any means. The article makes it breathlessly sound like enabling this feature in the developer menu (something everyone likes going into) will magically upgrade a 320kpbs/44Hz mp3 to 1Mbps/96Hz quality, which is, charitably, a farce. Maybe streaming services support this? Why use less mobile data to listen to music when you could use more in noisy environments?
Pixel market penetration isn't going to cause a gold rush to include the feature on all things audio. That said, Pixel owners are probably statistically more likely than other Android users to be aware of hi-def codecs, but it's still a Venn diagram that isn't a circle.