slam dunk, have you actually read the thread?
ATC DO NOT have the DF capability on any other frequency. They generally welcome the practice. If the only thing to happen was "Thank you for your Practice Pan - goodbye" then I would agree. However, there is rather more to it than simply coming out with the correct info on the Pan call.
It is a gross oversimplification to say that "Emergency channels are for emergencies only". Emergency procedures need to be practised. And a significan part of the practice cannot be done on any other frequency. So allow people (ATC and student pilots) to practise them.