Crouch dsmash out of run and pivot dsmash are both really good for the scenario (hitbox is active on frame 6 after input is registered)
ending combos with smash attacks is also really good so, situationally, op is right, if an opponent hard di's a high hitstun move, or is coming down with an attack without stage control (you'd be looking to trade here), the fsmash out of run is definitely good. In certain situations you can use it as an option select where you'd CC an attack into the smash attack (for example, running for position, CCing fox side-b, into fsmash punish), but in that situation the frame data really starts to become important.
but @OP I've definitely seen the technique used in bracket so, it's good that you're exploring your whole option spread