"No, that's not right. If there is a small fire just starting to put
out a little bit of smoke, that smoke will tend to rise. It would
collect significantly at the highest spot it can reach, first. Thus
code calls for installation there. "

I don't believe code requires that a smoke detector be installed at the
highest spot, only that there is at least one for each level of the
house, including basement. I've lived in a couple of homes that were
new construction and while both had smoke detectors wired together and
on each level, there were clearly higher areas in both where the smoke
detectors could have been installed, but weren't. In my current home,
there is a cathedral ceiling and the smoke detector isn't there.