I have an issue with stating any specific diagnosis is always a specific level of complexity. Let's use your example of vomiting.
Patient 1 - 14 y/o presenting with mother who vomited once yesterday after watching a disgusting video his friend showed him. No vomiting since, no nausea. Keeping down fluids and light foods. Doc advises to continue light foods for next 24 hours, then resume regular diet. And to stop watching disgusting videos.
Patient 2 - 75 y/o who vomited 7 times over the last 8 hours and unable to keep down any fluids. No nausea. No data/testing ordered or reviewed. Doc advises to proceed to ER for IV fluids and further evaluation. States "concerned about potential dehydration" but does not diagnose dehydration.
Both patients would have a diagnosis of vomiting R11.10, but not the same level of problem.
Don't forget "A problem that is normally self-limited or minor but is not resolving consistent with a definite and prescribed course is an acute, uncomplicated illness." So a cough for weeks, and requiring OTC or Rx is likely a more complex problem than straightforward.
For any problem, you have to take the problem as it stands today. Certainly, cough or vomiting may be self-limiting 90% of the time, but could be an acute uncomplicated, acute with systemic, or even possibly an acute that poses a threat to life (but you would expect to have additional diagnoses at that point).
You must level each visit based on the documentation for that visit.