I mean, sure, everything can be faked on the internet. It's all just data, even if this spoofer didn't exist it'd be easy enough to photoshop results. Anyone who actually walks into a thread and posts a spoofed result is a massive friend though.
why would anyone do this
Speedtest topics may as well just be classified as spam, we've had so many of them and every time it's just everyone posting their own speedtest with nobody even looking at anyone else's.