Mars is more than capable of clearing its neighborhood on its own, as seen by measures like the Stern-Levison parameter and others that have been derived from dynamics and simulation scalings. It isn't even close to being marginal.
Jupiter's Stern-Levison parameter is 1,38 million times larger than Mars's. No, Mars would not have "cleared its neighborhood"; it's well recognized in the literature that the majority of "neighborhood clearing" in our solar system was done by Jupiter and Saturn. There's lots of niggling over the exact details (here's one scenario), but there's no reputable peer-reviewed source involving orbital dynamics simulations arguing that Mars did the majority of work to clear its neighborhood. Heck, Neptune has a Stern-Levison parameter 290 times higher than Mars and it still has at least two bodies with around 1/50th the mass of Mars each in its neighborhood (and possibly even larger ones). If a 290 times greater ability to clear its neighborhood couldn't do it, why do you think Mars stands a chance on its own?
The whole "cleared the neighborhood" concept for planets is built on a bare falsehood: that the majority of them are actually responsible for clearing their own neighborhoods. The science says exactly the opposite: that the gas giants cleared the majority of bodies from our solar system.
Because some people care more about the dynamics of the planets and their orbits than what is on/in the planets. Even in geology on Earth, there are classifications for what makes up a mineral, and classifications for structures and locations they are found in.
Are you seriously trying to claim that, say, stilbite will be classified as a different mineral based on whether it occurs in Iceland or the United States? Minerals are what they are. The individual structures minerals are found in may have names (for example, the "Bakken Shale"), but those are just names. You know, like "Kuiper Belt".
Some geologists don't care where it came from as long as the make up is similar, others very much care if samples come from near the same location, even if they are very different minerals.
What on Earth are you talking about? If you're trying to say "Some scientists want to study the variety of objects in the Kuiper Belt and compare them to each other", then you already have a word for that: KBO.
You can go on and on about how dissimilar you think Jupiter and Earth are, but that doesn't change that there are metrics where they are much more similar than other rocky planets are to Earth.
You can't be serious.