Not a false assumption, it happens all the time. Heck, if you plan for
the worst case scenario all the time, just stay home and sell the boat.
If you try to put out a 10:1 scope with all chain on a calm day, you're
going to have a pile of chain on the bottom, and that's all. Probably
piled up on top of your hurricane anchor. You can look up what people
have learned over the years / decades for all chain rode and 3:1 is
just fine. 6 or 7 to one or more is used in storms. I didn't say NEVER
use that scope, it's just not necessary most of the time. Since the
original poster was only asking about scope, I limited mine to that
discussion. As a matter of practice, I have two anchors and rodes set
up ready to go on the bow, with 6 more in inventory for all kinds of
conditions, including hurricanes. 95% of the time, I stick with my
primary anchor and 3:1 scope. Advising someone to get the biggest chain
and anchor they can doesn't recognize real world conditions.