Neither was Nebraska. Both schools have initiated the process to become members of the AAU. I expect FSU to be accepted soon.
True that Nebraska wasn’t an AAU member when they actually started playing in the Big Ten (2011), but they were an AAU member when they were invited (2010).
OTOH, Miami is an AAU school. I have no idea of their interest in moving from the ACC and/or the interest of the Big 10 of extended them an invite.