Okay yeah, I messed up when using lockfile. I misread

Unlike the Windows msvcrt.locking() function, the Unix fcntl.flock(), fcntl.lockf() and the deprecated posixfile module, the API is identical across both Unix (including Linux and Mac) and Windows platforms. The lock mechanism relies on the atomic nature of the link() (on Unix)...

to mean "still has the properties of flock"