But to answer your question seriously. Is a river today the same it was before? Is Firefox today the same it was when XP roamed the Earth with the dinosaurs?
The answer is, no, and yes, some of it. So it's a cheeky way to point out that someone managed to get Firefox running on a presumably very different OS HaikuOS, before getting it to run on Windows XP, which arguably must be pretty similar to say, Windows 10, when it comes to Win32 APIs.
(But of course, also Windows 10 is a slightly different river to the Windows XP creek.)