IMHO, the 'ro' is the right thing to do if you want to run fsck on boot otherwise file system faults may not be recovered. So that we should leave it as default than 'rw', and if we really want 'rw' boot option we should specify it on GRUB_CMDLINE_LINUX= or such to override that default (ro). That was my understanding in the past but with new systemd maybe it think or was implemented differently ? Thanks.