An alternate way of looking at it is to define "Exp" as the most general form of advancement available (as it traditionally applies only to character level, which traditionally advances numerous aspects of the character at once). This would exclude "skill-specific advancement" entirely, as even when skills or other character attributes use points to measure advancement, it's usually entirely separate from the basic Exp which advances character level.
By this reckoning, the two tropes would be:
- Do something other than combat in order to get better at combat (and possibly everything else too).
- Do something entirely mundane in order to get better at combat (and possibly everything else too).
The third situation, of "doing something specific to get better at that specific thing" would fall outside the scope of "Exp", since that's a more "realistic" and thus less tropeable mechanic. In addition, Rare Candy
could count as either of the above tropes, depending on where it comes from: if the advancement item can only be obtained via combat, it's an extension of advancement via combat. If it can be obtained through non-combat effort, it's #1 above, and if it can be obtained without effort, it's #2.
To summarize: getting +1 combat for going fishing is probably a trope, and getting +1 fishing for going fishing probably isn't.