I would never use whip stitch to put up a hem....herringbone all the way or if it's in silk then a rolled hem is more usual.
I only use the hidden ladderwork stitch if I'm sewing etuis or maybe closing a seam on something stuffed.
Hexagons are whip stitched together to keep the stitching tight and the seams, even if they've been cut on the diagonal, all the same length. They don't move or stretch. Ladderwork eases slightly since in effect its really just a running stitch worked sideways.
If it works for you; fine
by the time whip stitch is properly seated the fabrics are almost impossible to seperate though.
Like Auntiepiggylpn the actual stitch through is straight, with the tiny little diagonal lying on the underside across the seam.
Until very recently I had never made patchwork any other way than over papers.
I'm finding machine patchwork a right royal pain in the backside to do accurately, and a major frustration to get anywhere near as neat
it's an awful lot quicker though
Another advantage with papers is that even if I've put my sewing away in a box, I can pick it up months later and it still just flows together, piece after piece after piece, and they all lie flat and even.
Mary