A website may remember a display preference even when you have not created an account. One possible mechanism is browser local storage. MDN explains that localStorage keeps data for an origin across browser sessions.
Separate local memory from account synchronisation
A setting stored in one browser is not automatically a setting stored in an online account. If it disappears on another device or browser profile, that difference may be consistent with local storage. The exact behaviour depends on how the site is built.
Do not assume every remembered choice uses this mechanism. Cookies, server-side account settings, and other storage systems can also be involved. The visible result alone does not identify the implementation.
Check before clearing site data
Removing a site’s stored data can reset preferences or remove locally held work, depending on the application. Read the site’s own guidance and preserve anything important before using a broad clearing action as a troubleshooting step.
For a simple observation, change a harmless setting and note which browser and profile you used. If you later report a problem, include those details. They help distinguish a missing local preference from a failed account sync without claiming that all websites store or restore settings in the same way.