Earlier quoted context omitted.
Since corporations are people, they should be able to plead the 5th as well.
Sure, but in this case Apple isn't being accused of anything so the 5th amendment doesn't apply.
This is a criminal case, however. It would apply to real people, but likely does not apply to corporations regardless of rulings treating corporations as people for other purpose. I imagine the Apple lawyers would have had it as part of their defense strategy if it did.