What do Fighter pilots' thumbs look like? I have to imagine this question doesn't get asked too often, but I read actress Sienna Miller said her "nipples look like fighter pilots' thumbs" from breastfeeding.

I'm so confused. Do pilots' thumbs have a certain way of looking that is known?

I'm a blogger and want to write about her comment, but I'm looking for some context to explain it to our readers with.

Any ideas?

http://www.eonline.com/news/844242/sienna-miller-prefers-her-postpartum-nipples-they-look-like-fighter-pilots-thumbs
In some fighter aircraft there are several functional switches on the control stick--switching from guns to missles and vice-versa, aircraft trim, firing the weapon(s), etc. A fighter pilot's thumb can get a real workout and over time that could result in a very muscular thumb.