I suppose this depends on where the website operates and what they are legally required to do...
In Canada (or at least most of Canada) analytics isn't required to provide an opt-out... I work in media, and from what I have seen from a lot of media companies is that we have opt-out for advertising cookies, but not for analytics cookies. While Quebec has stricter rules, since many of the English media outlets don't do direct business in Quebec, they either do a specific opt out policy for Quebec, or again, if they don't really have operations or products targeted to Quebec they just put in the legalese that analytics is part of the website and therefore not included in the opt-out.
Now, depending on your implementation, in the old AppMeasusement.js for AA, not setting an ECID, and forcing the s.vid and s.fid cookies to session based allowed tracking to continue without setting "fingerprinting cookies" during an opt-out scenario...
However, the webSDK doesn't seem to offer anything equivalent to this for some reason... which personally seems like a miss. If the opt-out is specifically around cookies that "follow" a user, this does not mean that you need to opt completely out of tracking (unless the opt out specifically gives the option to opt-out of tracking in general). I very much disagree with that approach, as opting out of cookies is very different from opting out of tracking.