Well, your right on both parts. the industry does at times give girls with, shall we say, 'limited' backside a nice camera angle to show her as a girl with booty.
I define 'booty' as a girl whose backside is instanly Recognizable. Doesn't always mean big.
Just a girl whose ass gives her a bubble butt because of it's relation to her size.
For example, Megan Reece. Some would say her ass is big. It's not really that big, but for her short stature, it sticks out a bit more than alot of girls her size.
Other than that, I also define booty as your first quote does; "a really thick and big ass capable of crushing your dick beneath it and which jiggles like a pendulum?"

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