gcsfuse doesn't have streaming?

I'm currently running into a problem where:

I have an application trying to append logs to a particular log file inside of a mounted dir. Whilst the program is running, I cannot see the item being loaded into GCS. However, when I stop the program, it appears to have been uploaded. I've done `du -sh /mounted_bucket/app.log` and the size is growing & increasing.

I then tried to run the exact same program and when I stopped, the file size just increased.