If the immediate family of the person donated it, sure.
But even still, it’s not about what my opinion is. They have a committee who reviews these things case by case, and they’re making recommendations about their archives based on historical context, educational value, and the individual being studied.
edit to add: Gage himself engaged with Harvard, and he wasn’t held against his will. He knew he was a subject of analysis, and his family willingly donated his remains to an educational end. The two are not comparable in any way, shape, or form.