HIPAA doesn't cover airlines. It's a privacy thing. No one else has the right to know your personal business. People want answers for stuff all the time, but I'm not sure how providing that info benefits DL. "Someone is disabled." Then you get on the plane and decide that the person isn't disabled enough and make a stink about it. "Accommodate a VIP" Then you complain that your money matters less. "Security" Then you get on the plane and harass the security people. There's nothing in sharing that benefits DL.

Schedule changes can also do it. While the plane may not have changed, seats can be switched if the plane changes at any time, even for a moment on SCS.