This is very possible and kind of the whole point of the post.
Since the distinction between underground and alternative doesn't seem very intuitive to me.
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Not at all what I said. There is a difference between having similar production and theme and sounding the same all together.
Surely to say that most of these tracks aren't highly similar in themes and production would be ignorant wouldn't you agree?

I was talking about the similar production styles and themes regarding a term such a underground, which when usually when associated with art is an umbrella term for innovation and non-mainstream.
In this case most of the songs here fall under a very similar style and theme. Which would point towards the term underground mostly used as a genre specific term, rather than it's usual usage.
And a few of these songs are quite mainstream (millions of youtube views can hardly be called underground in many peoples eyes).

The usage of the word underground is what I'm trying to wrap my head around , nothing about the songs themselves. When talking about underground music, usually it's associated with multiplicity.
Surely most of the stuff posted here has variety, but in most cases variety inside a very specific style of hiphop. Why is the word underground different in hiphop?