On a turboprop engine, a "Torque setting problem" is the same as a "Throttle setting problem" on a piston engine.
On a piston engine you set RPM or MP (with the power lever); on a turboprop engine you set torque (with the same power lever) - usually,
AFAIK. On a turbojet you set some other stuff.
It would not be in the PPL(A) general knowledge stuff, but I can sort-of imagine a TP pilot hoping ATC would know what it means. Similarly, one might expect them to understand that e.g. a "landing gear hydraulics leak" is something relatively important.
One could argue he should just have declared an emergency, but ATC do sometimes probe reasons e.g. if you simply request 20 degrees left they are likely to check whether it is "due weather" to make sure you are not trying to get a shortcut which they would not otherwise give you. So I can see a pilot stating more details of a problem than he actually thinks ATC will understand fundamentally, just in case they query it further. Or an airport might deny a (non Mayday) landing clearance because they have not received PNR for Customs/Immigration (I have had that), in which case one would obviously declare a Mayday immediately but a lot of pilots don't want to do that.
I would have used the sdame expression if I had the same problem, but only to properly English speaking ATC. In Spain/Italy I would just say I have an "engine problem".