If you set filesystem check on logical volume you cant see any stats showing up.
In case of LVs simple call to realpath(3) (from brief look into the source) doesn't work.
check filesystem var path /var
with /var being a LV:
mount | grep var
/dev/mapper/main-var on /var type ext3 (rw,relatime,data=ordered)
leads to following error:
filesystem statistic error: cannot read /sys/class/block/main-var/stat -- No such file or directory
In case of logical volumes you have to translate LV's name to kernel device name (dm-?) first.