Yaku are just patterns, that have a different han value. If you look at Tenhou’s manual, you’ll see a list of different yaku, sorted by han value. The EMA score sheet – which is shit for other reasons – do not support your theories. If you look at it closely, it says:

One yaku – Iihan yaku (Ryanhan yaku, and so on, for the others)
This is their stupidity shining through – Their romanized japanese name of it even supports “One-han Yaku”, but they’ve decided to list them as “One yaku” instead, for some inexplicable reason. So, EMA’s scoresheet has a mistake which you base all your information off.

Oh, and the “double riichi = 2 yaku” is a bit confusing in retrospect… basically it’d be “riichi = 1 yaku”, “double = 1 yaku”, “ippatsu = 1 yaku”, so a “double riichi = 2 yaku” might have bit a tad confusing (but not inconsistent).

This is really all just straight from the european mahjong scoring ruleset I’ve been using as the basis.

“There are a number of classes of special hands worth 1-5 yaku, which give you 1-5 fan respectively. Dora also count as extra fan.” – Are you saying that chinitsu = 1 yaku, 5/6 han? Tanpin = 2 yaku 2 han?

Also, in episode 2 you put a note saying “double riichi = 2 yaku, ippatsu = 1 yaku.” So I assumed that (at that point?) you were getting them mixed up.

Sorry.

It could get confusing when talking about hands.

“the way I am interpreting the scoring rules is that fan = point doubling score, and yaku = special hands.”

What you said:

“Yaku = the “patterns”/hands
Han = “multipliers” or whatever you want to call it.”

And the difference is?