I'm running QB64-1.2 on Windows 10, because I had a problem with _MOUSEMOVEMENTX/Y in 1.4.
Could definitely be some legacy bug. Ran the program again (the one from the wiki) and had memory increase from 40.1 MB to 52.2 MB over about ten minutes, and it was a pretty gradual increase throughout. I'd say this is kind of insignificant, but it looks like the same issue is getting magnified on my other program and causing a lot more memory to leak--or something, idk. I'm going to try it in QB 1.4 and see how that handles...