it seems to me that the only newsgroup that was blatantly off-topic
for the post was r.a.owning.

I agree that it's arguably on topic for most of the groups, but so is
almost *every* topic. After all, what doesn't apply to the "piloting"
group? And aren't we all "students" of some sort?

The overlap of readership among the groups makes cross-posting
redundant. My observation is that it's mostly newbies that do it.

Of course, your original reply was somewhat exaggerated as well

Artistic license? ;-)