Carpenter v. United States (5-4)
Collins v. Virginia (8-1)
Barnes v. Felix (9-0)
These are all Supreme Court cases that were specifically about the 4th amendment and happened in the last 10 years.
The 4th amendment is over 200 years old and yet requires constant supervision by the Supreme Court to define the word reasonable or to police the lower courts understanding of precedent.
So you are wrong, with whatever presumption you are making that the word "unreasonable" is well defined.
The entire point of my post -- nay, the entire point of the jury system in the United States -- is that until a jury is empaneled, the word "reasonable" may as well have no meaning whatsoever. No one is ever going to define that word short of a jury. You may think you know what is reasonable, they may think they have set forth reasonability in the law, but the only judge that's ever going to make an applicable decision on the word is a juror.
The Supreme Court may decide whether a reasonable jury could have come to a certain conclusion (about whether something was reasonable) but the Supreme Court is also not the place to look for this definition.
Good luck in your studies.