Crab is primarily protein, while pineapple is sugars & starches including fiber.
How different foods look on a plate doesn't matter to your stomach & intestines. Protein, carbohydrates, and fat matter there. Your body will release different enzymes to snip the big molecules apart.
No link, nutrition educator in real life, college credit in knowing this stuff but not willing to dig out a textbook on a Saturday morning.
I trust the autopsy report on this. Remember that these folks take graduate courses in things like stomach contents.
(I don't wanna watch the slide show on that one, nope.)
jmpo ymmv lrr