Interesting article from Stringgeekery blog on multiple YOs:

“The important thing to realize is that when there’s a double or triple yarnover on the right side row, it doesn’t actually increase the knitting by that many stitches. It just makes a single large new stitch. It’s the number of stitches worked into the double (or triple) yarnover on the return row that makes for more than the single increase. Having multiple loops makes for an reminder of the location for multiple stitches but there’s no inherent reason to have them.”

Source: The physical size of multiple YOs