Impersonating a user can get confusing, especially if you're like most developers/admins, and have multiple tabs open all the time. Impersonating a user in one tab, effectively impersonates the user within your entire session (all windows/tabs). However, the issue here is similar to what happens when you change update sets in one tab without refreshing the others. If you impersonate a user in one tab, that tab refreshes to show your impersonated user account in the top-right, but if you don't reload all other tabs, you might be confused as to why you don't see the content you'd expect there.

Instead, many admins/developers prefer to open a new inPrivate or incognito window, log in there, and impersonate the other user only in that window, as that will not impact your other browser windows. This way, you can have two windows side-by-side, both with different user sessions logged in!