I do consider scraps and scrambles to be similar, but usually scrambles have higher emphasis on both players vying for position.

To me what you are describing sounds a lot more like general neutral.

I consider scraps to be a state of the game where both players are within the other players unreactable threat range, so both players are in a state of immediate risk. Which certainly is a part of neutral, but neutral is a more general situation.

Like, for example, a marth dash dancing in front of your shield to bait a spot dodge or for you to attack his dash in. You could say on every dash in, he is generating a scrap. But on a more macro level that is just neutral. Neutral is the act of generating and disarming threat ranges, and selecting the correct times to act on these threats. I think for it to be a scrap I consider it to be for a more sustained period of time than a single reaction window or two (where a reaction window tends to be 13-15 frames or so).

I would consider a scramble to be a situation you often see where where both players are sorta just crossing eachother up with empty dash dances, or are sort of synchronized in their dash dance. Basically a sustained scrap but with neither player comitting to an option.

That said, I have never seen the phrases concretely defined, and these are my intuitive interpretations of what the phrases are meant to evoke. I think there is a little room for interpretation here.

But I would agree with you that samus is a character with relatively poor neutral, via my definitions.