[mkl]

I think this is right. In ten years of use, the handful of times the plain Ian Knot has come undone on me were from stepping on and end or similar - it's never come undone without some external force, and even then it's usually fine. I just checked and I'm not doing the Granny Knot version.

[jamesgeck0]

It depends on the string you’re using to tie it. Paracord shoelaces are more slippery than most; I had to switch to the secure version of the knot because the normal one didn’t have enough friction to stay tied all day.

[hamandcheese]

I believe it’s impossible to tie a granny knot using the Ian Knot method.

[mkl]

It's definitely possible. It depends on which way you do the initial single knot (right over left or left over right), relative to which way you turn the Ian Knot loops (left end towards you or away). The are four possible combinations, two of which produce Granny Knots.