One can call interface functions on just an Actor. The whole point here is inter-class comms without casting, ever.
Combine it with inheritance and you’ll never look back at the tight direct comms. At this point your opinion is borderline misinformation, ha. You’re simply not using it correctly.
Judging by the colour of the pins on your node, you’re attempting to call the wrong thing to start with. You’re not calling interface function. You’re calling local implementation. As in:
More info here in the Calling Interface Functions on Other Blueprints section: