Is that true that mentally unstable women/men are better in bed and why?

My brother once dated a bit of a crazy girl who was very pretty and when I asked him,

“Aren’t you scared, she’s obviously a bit psycho.”

He said “I know she is, but those are the types of girls who are the best in bed.”

Updates
7 mo
Edit: They weren’t dating.

That girl was visiting my brother for sex.
Is that true that mentally unstable women/men are better in bed and why?
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