But now I am a little confused, how does less grip not equal less wear?
Less grip = more slippage
When you have slippage, you are removing bits of tyre ( hence the black marks on the asphalt)
like sandpaper on timber if you let it slip it removes bits of timber if you don't move it your timber stays the same.
Apologies if that sounds a bit patronising, just trying to paint a picture with words.
The centre of the tyre will wear more as that small contact patch has to deal with the forces of acceleration and decelleration.
You'll notice this particularly on car tyres that are overinflated, they'll tend to wear in the centre whereas underinflated (which is more common) will tend to wear the outside of the tread.