Depends what you consider "higher" Reece. LOL! To me, the closer you are to the nut/tuning pegs, the lower the notes. That's considered "lower on the neck". As he goes up towards the 12th fret, the notes get higher in pitch...higher on the neck towards the pick-ups. :)
What happens is, our ears get used to a certain sound in a lower register. When someone makes a drastic change for example...and plays something an octave higher, and stays there, it gives the impression of "the bottom dropping out". There's no meat in those upper notes for a bassist unless he's soloing, thus, all the bottom goes away.
This sort of thing was more acceptable in the 70's and earlier, but today due to all the low tuning and how thick mixes are, as soon as that bassist goes up for too long, it just sounds like the whole bottom dropped out. Especially if the bassist has a good tone like say, John Entwistle. He at times had that beautiful, low note, almost piano sounding bass tone. This low end is so awesome that once it leaves, all the bottom leaves too. As long as he doesn't stay up on those high notes for too long, it's cool, but quite a few guys do this and stay there too long. When they do...there is no bottom other than the kick drum. This to me leaves the mix sound empty...kinda like the bottom of a floor dropping out.
I have nothing against high notes on a bass, I just don't like how the bottom drops out completely. It's more an "ear getting used to the nice low end" really. If the tune didn't start there and had high notes to begin with, you don't notice it as much. But man...once you get used to the lows and then the dude goes up high, it just sounds empty to me and affects the impact of the song.
-Danny