Not a programming expert, but far as I understand, /fopen loads the file in memory and /fclose writes it back to your HDD. So if another application uses the file before you did /fclose, any changes you may have made to the file won't be seen by that other application.
Thats generally the way it would work, however someone said it doesn't buffer it, which means as soon as you /fwrite it writes it to the disk, not when you /fclose. Hopefully an option to buffer it will be in 6.11.
