Using Blueprint input in template

I’m working on converting an automation of mine to a Blueprint, the automation itself sends a notification that a lock has been unlocked for x using the template {{states.lock.front_door.last_changed | relative_time}}.

In my Blueprint I have

  lock_entity: !input lock

which works great when I use it like {{state_attr(lock_entity,'friendly_name')}} but not when I try {{states.lock_entity.last_changed | relative_time}}. It instead returns None. Any clues on how to effectively use the variable (or the plain !input lock) in the template to get the last_changed value?

If you have lock in HA, you can recreate this simply in template tab of Developer Tools with

{% set lock_entity = 'lock.back_door' %}

Works: {{state_attr(lock_entity,'friendly_name')}}

Returns None: {{states.lock_entity.last_changed | relative_time}}
{{states[lock_entity].last_changed | relative_time}}

I was so close, that did the trick! Thanks!