Sure, but it's IMHO clearly arguable where that line is. The underlying engine is only a part of the user experience of a browser, and browser based on a common engine are commonly described as different products.

Chrome, Chromium, new Edge, Brave and Qutebrowser all use the same engine, but even the first two are not uncommonly considered to be different products. Same with Safari, Chrome and Firefox on iOS, despite Apple only allowing their own browser engine on iOS.