To be fair, the article mentions reading via which elements are 'full', and I mention by the 'crease point'.

When I started parachuting, I struggled to quickly read windsocks, because the definition of 'full' can be somewhat ambiguous (Is it mostly / somewhat / completely inflated, what if it's full now but wasn't three seconds ago..)

I'd found: See where it 'breaks' provided a much better point of reference.

Perhaps this will help others that shared my confusion :)