Earlier quoted context omitted.
Is there any reason to suspect it's something besides the person behind the content requested their domain be excluded? Or IA behaving as they legally should and always have?
Yes - the Archive's refusal to provide a reason. They don't get to have both the privilege of opaquely excluding content, and the assumption that all exclusions are for the most faultless reasons.
Are the content owners complaining about a desire to be archived but IA is blocking them? As if not, I don't see the issue.