You are correct (for standard Japanese 標準語 hyoujungo; other dialects can be quite different). NoneOfUrBusiness's response is not a great take. Every word has an accented syllable or no accent at all (and it really is based on syllables, not mora). The accent is realized as a relatively sudden drop in pitch after the accented syllable with no (necessary) change in length or loudness. The drop can complete within the next syllable or after. Usually at the beginning of an utterance you start low, climb up in pitch to a certain point, and then either hit an accent and drop suddenly or gradually drop across a longer period of time if there's no accent.
The precise pitch does not matter, and it's definitely possible to have two accents close together resulting in a high-mid-low kind of pitch pattern.
Things are also complicated by the fact that Japanese likes devoicing certain syllables. Devoiced syllables can still be accented even though they can't carry pitch in the same way as voiced syllables.
I think he titled it 7 because he explicitly presents 7 different cases. I'm not sure what you mean by saying three are the same though? Two are obviously exactly the same. Personally, I would only consider it three different "things":
I think it's fair to even say that it's almost exactly one thing: an instruction to let air out of your nose whilst producing the surrounding phonemes.