Testing sunset actions through the offset

I am testing an automation based on sunset and it is past sunset where I am now.

I therefore tried to use (in a new app) run_at_sunset(cb, offset=3600) - the intent is to have the trigger started one hour after sunset, which should be in a few minutes from now where I am. But once this hour passes, the callback is not triggered. OTOH a call with run_in(cb, 5) runs the callback fine.

My question: is a run_at_sunset taken into account once we are past sunset, when used with an offset? Or does it have to “cross” the sunset and then an action is scheduled for after the offset?

In other words, can I test past sunset actions by meddling with the offset pas sunset?

(I know about time travel, I just do not want to perturbate my current setup is possible and test as above)