Those are two very different things!
Locked critical partitions means you can’t flash any of the critical partitions, that’s not directly tied to the state of your bootloader (you loose that ability if you lock the bootloader though).
You should not have a locked bootloader however if you plan on installing iodéOS.
As long as the OS you are installing flashes the frp partition, not sure if iodé does, you will end up with get_unlock_ability=1. Just make sure you check the state after flashing and don’t lock it if it’s 0.