Ahhh...now I understand although the patch comments don't seem to match those in man tune2fs which suggests that relying on the kernel to detect file system errors may lead to data loss:
You should strongly consider the consequences of disabling
mount-count-dependent checking entirely. Bad disk drives,
cables, memory, and kernel bugs could all corrupt a filesystem
without marking the filesystem dirty or in error. If you are
using journaling on your filesystem, your filesystem will never
be marked dirty, so it will not normally be checked. A filesys‐
tem error detected by the kernel will still force an fsck on the
next reboot, but it may already be too late to prevent data loss
at that point.
It seems strange to me that the default behavior wasn't left alone (periodic fsck checks enabled) as this seems much safer than just disabling this feature for everyone.
I think I'll re-enable in /etc/mk2fs.conf just to be safe.
A big thank you to all who replied