Bingo!   There’s a solid technical reason for paying close attention to file-handles ... buffering.   Until a file-handle is closed, it is possible that there’s some data out there which has not been written to disk.   Other applications will not see that data yet; nor will this application, necessarily, if it opens a second handle to the same file.   (Which it is, of course, free to do.)

Obviously, the system will wipe your a*s ... clean up after you even if you don’t, but writing to a file is an action that you need to explicitly bring to a close.   Reading from the file is much more forgiving.