I knew a college level Greco-Roman wrestler from Nebraska who lost a Jiu-Jitsu fight because he gave up his back. In the first fighting style, it's a valid technique to prevent getting pinned. In the latter, it's practically begging to get choked. Learned instincts are a real problem.
Athletes who have wrestled often have a tough time learning BJJ, initially. A lot of the skills they learned in Greco-Roman will translate very nicely into BJJ, but as you said, a lot of the instincts developed in wrestling will get them into trouble.
Younger wrestlers that start coming into BJJ can be amusing to watch panic when put on their backs. Every fiber of their being is demanding that they ferociously struggle to avoid having their shoulders touch the ground. Experienced BJJ fighters will use this. Let them panic, let them tire out while trying to free themselves from a mildly dangerous position... and then put them into a truly bad position.
Of course, if a wrestler really dedicates himself to learning BJJ, they are very capable. They already have a great grasp at controlling other bodies, and a great understanding of body mechanics. They also have this mental toughness that comes from being placed in uncomfortable, often painful positions and having to fight their way out. It can all come together to form a truly spectacular skillset.
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