Relative_time is broken for attributes

Looks likes relative_time is broken now when working with entity attributes,
I know I can change to “manual” calculation using as_timestamp(now()- … but maybe anyone have better idea before I submit an issue on github?

{{ 
  strptime(
    states.variable.last_boiler.attributes.last_off,
    "%Y-%m-%d, %H:%M") }}
// 2020-10-16 10:02:18.015694+00:00

{{ 
relative_time(
  strptime(
    states.variable.last_boiler.attributes.last_off,
    "%Y-%m-%d, %H:%M")) }}
// 2020-10-16 10:02:18.015694+00:00

{{ 
  strptime(
    states.variable.last_boiler.last_changed,
    "%Y-%m-%d, %H:%M") }}
// 2020-10-16 12:55:47.823933+00:00

{{ 
relative_time(
  strptime(
    states.variable.last_boiler.last_changed,
    "%Y-%m-%d, %H:%M")) }}
// 23 minutes

Yes, that’s odd, for me it works sometimes, i.e.,

relative_time(state_attr( 'vacuum.robo', 'clean_stop')) 

Sometimes I see the time in minutes or hours and sometimes I see just the timestamp like this

2020-12-30 12:14:56+02:00

by the way the time stamp itself is:

state_attr( 'vacuum.robo', 'clean_stop') = 2020-12-30 10:14:56