[sciurius]

in order to support a user copying in a new version of a file,

Great! I didn't dare to hope that you would support this.

Due to that fact, I always have to query for every file to check it's last modified timestamp to see if it's changed. That's probably what is taking 10 minutes.

You can get all the metadata of all files in a folder in a single call, and cache it locally?

The timestamp in the hashcodes file is in milliseconds. Does GDrive use milliseconds as well?
Do you issue a separate call to update the timestamp on the drive to the value in the hashcodes file, or vice versa?

A better label for the setting would probably be "Check for updated files in cloud folders".

Nice!