10W: but it's all words innit? As you say it was in place before anyone called them TMZs, but although its establishment followed a different path, it has exactly the same effect - if someone asks one of your guys for a clearance above 6000ft in the TMA, they will immediately be asked to squawk, and if they say "negative transponder" you will probably keep them out until you sort out whether the traffic situation permits a non-transponding transit.
I guess on the same basis all UK airspace above FL100 is a TMZ.
NS