Why would the music and style be treated as more special than the concept of the game ?

They shouldn't, but the complexity required to be considered different is usually less. For example you probably wouldn't say that Crash bandicot is a clone of Mario Bros, even though both are 2d platformers. But for music or images even if they are only half the same they feel like clones.

Also depends on how 'concept' is defined. Two games where you "unpack things" can be vastly different, but two games where "you unpack things from a packing box and place them on small diorama-like rooms without any objective" is hard to differentiate.

All assets have degrees of genres (platform/shooter/..., rap/classic/..., pixelart/medieval/...). But the amount of things you need to change in order to create an "original work" is not the same for all of them.

>For example you probably wouldn't say that Crash bandicot[sic] is a clone of Mario Bros, even though both are 2d platformers.

Ehm, I don't know whether this supports or hurts your argument, but Crash Bandicoot is 3d (or at least 2.5d) and has an entirely different type of gameplay than either the 2d or the 3d Mario games.

You're right, I was thinking of the 2d sections, but even those are, as you say, 2.5D.

Maybe Megaman is a better example?

Yeah, I suppose that works. It is 2d, but has such vastly different game mechanics that no one would argue it's a clone.

Assets and production are what differentiate one game from another. "Concept" more often than not is just a genre marker.