Earlier quoted context omitted.
That page says, "Requires Google Chrome or Firefox," and the download link takes you to the Chrome web store. I'm not sure the poster considers that full support.
That's somewhat fair, although the 1Password X page (which is what AgileBits calls their in-browser version) describes it as being comparable to the native versions, which to me goes against OP's statement that > full functionality can’t be dependent on an app which is only available on Mac OS and/or Windows. The existence of 1Password X means that full functionality is not _dependent_ on a MacOS/Windows app. The arg…
If the 1Password X claims that its functionality is comparable to the native version, then it is lying.