Yes I know it says that, but sometimes there's more than one way of doing things. Look on the glossary page for ptbl video; it's tricky, though not too bad if you pick it up from front to back. That's why I was suggesting picking up the yarn from back to front though and that way you can purl into the front loop, not the back. It will still twist the stitch which is what you need to do for this kind of increase. You can also use a backwards loop for a m1, you just wrap the yarn around the needle and don't work it until the next row.
sue- knitting heretic