Yes the default repair option is preen, which basically means only make minor, “safe” changes that don’t carry a risk of data loss, such as cleaning up orphaned inodes, and replaying the journal.
Because ext4 is journalled many types of “minor” corruption like this can be repaired safely by replaying the journal. These minor types of corruption won’t actually cause you any operational problems though, and would have gone unnoticed.
However without fsck.repair=yes more severe corruption will still trigger systemd’s emergency mode, and it is this type of severe corruption that leads to a system booting in read only mode or causes disk IO errors that cause updates to fail etc that cannot be fixed by preen mode. So any real problems that would have caused you actual issues won’t be fixed by preen.
Before the September update this would have taken you to a prompt asking you to enter the root password to login - which is not possible as we don’t set a root password, so you would be stuck. Since the September update you will at least be taken to a command prompt where the problem can be manually repaired.
However for a device that usually doesn’t have a keyboard connected and is intended to be used somewhat as an “appliance” this is not very user friendly.
Don’t worry, automated fsck support is very high on our priority list, and we were hoping to have it ready for this release but other things have intervened, and there has also been a bit of internal debate about the best way to do it.
For anyone who wants to enable an automated fsck with repair right now all you need to do is edit /etc/fstab and change the second number at the end of each line from 0 to 1 (systemd doesn’t make any distinction between 1,2,3 etc, so using numbers above 1 makes no difference) then edit /boot/cmdline.txt (/boot/uEnv.txt on a vero) and on the end of the same line add a space then:
On rebooting you should see a two line fsck scan in the top left corner of the splash screen momentarily during boot. When no repairs are needed it only takes a couple of seconds.