It seems like the core things that Anki needs are new user experience improvements, and algorithm updates. SM2 really shows its age as compared to other algorithms.
For me really learning a word means:
(1) Knowing how to say it.
(2) Knowing how to write it, meaning the Chinese characters, of course.
(3) Still remembering (1) and (2) after at least a month.
(4) Being able to actually use the word correctly.
You learn the words for a day (you're able to match the sounds and meaning to it). You will forget a lot of them tomorrow, so now you have to re-learn them. This is just how Anki works. You keep learning and re-learning until they stick for a prolonged period of time. It's common for Japanese learners to add between 20 or 30 words to their learning queue.
If you understand how Anki works, you will also understand how the word learning is used in relation to its flashcard mechanism.
And with all due respect, someone claiming they learn 20 words per day, in Mandarin, is an almost outrageous claim. If you think that "learning" is commonly agreed upon to mean "memorize for a couple of hours", then please show me the research into the meaning of the word, that proves your claim. While I have explicitly stated, what _my personal_ definition is, you are claiming to be knowledgeable about a "commonly agreed upon" definition. That is an impressive claim in itself. Let us all hear that definition, that is so commonly agreed upon, so that we can gain from that.
What you call learning, I call "training" or "practicing" or "revising". Now the onus is on you to prove to me, that indeed as you claim there is some commonly agreed upon definition, specifically in the area of learning Mandarin, that proves, that my definition is off.
And I will have you know, that I am learning Mandarin for some 10+ years, and have a lot of experience in that area. I know what counts and what is important.
Why do you keep harping on Mandarin in particular? Do you think it's harder than other languages to learn new words? It's not like you have to learn new hanzi for every word. Most are compounds. It's like being surprised someone easily learned how to spell "lighthouse" because it's got a silent "gh" and a silent "e" and the "ou" is not pronounced the way you'd expect, and the "th" in the middle isn't pronounced like "th" should be.
The learner already knew how to spell "light" and "house" so it was effortless to learn "lighthouse."
My experience with Japanese is that you hit around 800 or so kanji and new vocab comes very easily. Even new kanji come extremely easily because they're all made up of the same parts ("radicals").
EdIT: One hour a day devoted to language study will yield 20 new vocab words a day that, over time, you'll have around 85% recall, which translates to over 6,000 new words per year (over 7,000 but then you adjust downward because of the 85% factor).
The issue is that people want to learn a language in five minutes a day, but they don't bat an eye at playing a video game an hour a day to be able to beat some level. I remember playing for hours to be able to get good at 1942 on the NES back in the early 90s.