No, jailbroken means that you make the device do something that manufacturer prohibits (breaking out of a jail). Unlocking the bootloader where the manufacturer supports unlocking the bootloader is using it as designed. The correct term is "unlockable bootloader", not unlocked. No one ships a production device with an unlocked bootloader.

I've only ever heard "jailbroken" as using exploits to take control of a device that is intended by the vendor to be locked down - hence, breaking out of jail. I've only ever really heard of it being a term on iOS devices - on Android it's known as "rooting".

Bootloader unlocked generally means that the vendor permits the execution of arbitrary operating system code, ie there is no jail to break out of.

I'd understand jailbreak as escaping the jail via some vulnerability of sorts, which might not even be persisting.

In fact If I saw jailbroken in a listing I'd assume it's because the device cannot have its bootloader unlocked.