If an encrypted system partition is configured during installation openSUSE
puts /boot inside of it. While this scheme has certain advantages from the
security side of things, it also brings an inconvenience of entering LUKS
password twice. This inconvenience can be circumvented through adding a custom
key that is used by system to access encrypted partitions; thus GRUB becomes
the only software that asks for password.

openSUSE wiki:
https://en.opensuse.org/SDB:Encrypted_root_file_system
http://web.archive.org/web/20190601195245/https://en.opensuse.org/SDB:Encrypted_root_file_system

Arch wiki:
https://wiki.archlinux.org/index.php/Dm-crypt/Encrypting_an_entire_system#Encrypted_boot_partition_(GRUB)
http://web.archive.org/web/20190522050457/https://wiki.archlinux.org/index.php/Dm-crypt/Encrypting_an_entire_system

So it is a feature request for an automated procedure during OS install. There
are no security drawbacks AFAIK.