I recently read a helpful answer on a question asking for clarification on the ways to say "if" in Japanese: と, たら, なら, ば. The link is here: Differences among -たら、なら、-んだったら、-えば, etc
According to the post, ば has the following rule: the later clause must be non-volitional unless a state verb like ある is used or the subjects of both clauses are different. なら is used when saying "Since A, then B" - A is an assumed context and B is a conclusion from A. This is supported by Tae Kim's lesson on conditionals: http://www.guidetojapanese.org/learn/grammar/conditionals
However, when encountering another website's take on なら and ば, I was surprised they grouped the two together, such that the rule on ば above applied to なら as well. http://www.learn-japanese-adventure.com/japanese-conditional-form-ba-nara.html
The only difference they seem to have stated was that ば is for verbs and i-adjectives, whereas なら is for na-adjectives and nouns. However, negative forms of verbs, i-adjectives, na-adjectives and nouns have ば (なければ).
- In that website, why did they state that なら followed the rules of ば?
- Why did they teach the V/i-adj and na-adj/N distinction between なら and ば?
Is there a way to resolve these conflicts?