Despite it has rw option. An extraction of fstab:
/dev/disk/by-uuid/0109cc2c-414c-42dc-8a99-3ffe529020fe /mnt/0109cc2c-414c-42dc-8a99-3ffe529020fe auto rw,exec,noatime,x-gvfs-show 0 0
This entry was created by the standard drives tool of lxde on debian.
rw
option on the mount is its Mode.