that's not what diagrammatiks was talking about, he's saying the uneven fret lengths are issue. It's not that hard to actually cut frets to the proper size, and no competent luthier should be messing that up. hemi frets have nothing to do with bound fretboards, it's just a really nice feature to have, plus they typically mitigate sharp edges on fret ends. You don't even have to do fully hemispherical fret ends to get the benefits, they just look really nice. When done properly there shouldn't be any issue with string slippage, if there is, that means they ended up removing a bunch of fret material they didn't need to.