And that's the process that was causing the IO? That seems strange I wouldn't expect that much IO at all with the move and it should be a lot of read and some minor activity for the log writing, but you are only doing INFO level logging which is not that much.
I tested some moves and I can't seem to recreate that.
Assuming you are the latest version of rclone as well?
With rclone move rclone will delete the files on the source - I guess that could show up as disk write - I'm not sure.
Also check your config, make sure that stuff is really going to google drive and you haven't accidentally pointed stuff to local disk by forgetting the : in the remote name.