But it's probably possible for airlines to do it locally on your browser, using cookies or based on your account or frequent flyer number. I don't how that would work on the back end though, whether it's changing fare bucket availability, adding surcharges, or something else. And of course it wouldn't work if you just didn't log into any accounts, switched computers or browsers, and/or used private browsing mode.
This is what I meant/was referring to.