It does raise an interesting question - if we (pilots) have an emergency or significant failure, you'd naturally expect us to tell the controller working us, since it may affect our subsequent requests or lead to some escalating problem.
A few years ago on my way into Prestwick (from memory I think I was talking to Scottish at the time) I had an alternator failure. I called ATC and told them this, telling them I was shutting off my transponder to save power. Whilst they were happy for me to turn the transponder off, the problem itself clearly alarmed the controller somewhat until I explained that the worst that could happen was that my radio stopped working - we dealt with it, although maybe not as well as we might between us.
But, I can't recall anybody ever giving me any training in what level of understanding of aircraft systems and emergencies I can actually expect of what controllers at what levels? I can explain things in plain english at length if required - and if I have a mayday-level problem I will with a clear conscience. In my case however, or that perhaps of this PA46 pilot, it's not a true emergency but nonetheless useful to inform ATC that there is a problem in case it escalates.
I'm not aware of a particular protocol here, but maybe there should be? For example in my case:
"Scottish Information, G-AB, be advised I have a minor engine fault which requires me to shut down my transponder now and may subsequently lead to a radio and lights failure, it appears unlikely to cause an engine failure".
Or the Malibu's case:
"Foxy Radar, G-CD, be advised that I have a minor engine failure which may affect my accurate speed and altitude control and increase my landing distance."
Either way, it does make a strong case for having controllers who have trained in flying to something similar to PPL level (although you could make a stronger case for perhaps something more tailored - say light aircraft to solo standard, a sample cross-country through a selection of airspace, couple of glider flights and jet jumpseat rides, handful of emergencies in a sim, and groundschool covering PPL air law, ATPL systems and nav?) Or does that happen already anywhere?
G