You make them sound like medical conditions, bravado! I am not sure that you could clearly define either of those things. I have seen many children (not talking about 11+ here) who are stressed, unhappy and unable to perform in areas where they were previously competent, but surely as a parent one is in the best position to know if a child is feeling under too much pressure.
One thing I do know about is self motivation though, as my DD has just come through GCSEs and was always very highly motivated. This did not prevent her from feeling stressed, at times overwhelmed, at times hopeless...isn't it part of the human condition? We all need safety valves. Personally I tend to think the more control we have, the more we set our own agendas and goals (as opposed to having them externally imposed upon us, for example by parents, in the case of children), the less likely we are to suffer from adverse stress reactions.
I like to think that children who are pushed by parents to achieve things they themselves would not be especially keen to do, will eventually rebel and find their own path and exercise their freedom. But I also think it is pretty hard to do, if you have been encouraged to do a particular thing almost since birth, as you wouldn't really know what the alternatives are! And small children are usually pretty keen to please their parents, so will go along with what is offered to them. If that is intensive harpsichord lessons or underwater equine gymnastics or BabyAlgebra, then I suppose that is what they can be interpreted as 'showing interest and talent' in.
Either way, if you are worrying that a child is showing signs of 'burnout', then quite probably they are. Or puberty.