Vercingetorix,
With deference to HDs experience, what is being pointed out is, that 15 miles with both aircraft on frequency and positively separated is a nothing.
The moderator is pointing out that this was not the case, and suggesting HD have a look at the D and G threads (and also here in ATC/ NoATC-TIBA- Your experiences) to see the Russian roulette a supposedly first world ANSP and Regulator are content to let the aircraft fly through at flight levels.
I would appreciate HDs comments, as they are usually pretty good.
What are you, his minder?