Linux exclusion of non permanent system files

tried these excluded from --exclude /dev/* --exclude /lost+found/* --exclude /media/* --exclude /mnt/* --exclude /proc/* --exclude /sys/* --exclude /tmp/* --exclude /var/cache/apt/* from post Lack of Documentation on how to do a full system back up
and now i see

lock repository
no parent snapshot found, will read all files

Turns out the cause is --exclude /dev/*, if i don’t have it then using parent snapshot why?