Using そうです to respond to a sentence ending in a verb or adjective

Question

I was recently reading through grammar notes in the Japanese textbook, "Shin Nihongo no Kiso I", and came across a statement which confused me a bit:

In answering a question asked in a noun sentence, そう is often used as "そうです", "そうではありません". Use of そう is convenient as it makes an answer brief and simple. Note, however, that "そうです", or "そうではありません" cannot be used in answering a question asked in a sentence ending with a verb or in a sentence ending with an adjective.

This was the limit to which this statement was expounded upon. In what situations is this true / what sorts of interrogative sentences might the book be referring? For instance, I've definitely heard sentences like:

その犬は可愛いですね！　(That dog is cute, isn't it?)

Where the speaker isn't asking a "question" per se, but is certainly awaiting a response / confirmation from the listener. In this case, そうです / そうですね seem appropriate to me even though the sentence ended with an adjective.

Answer 1

I’m Japanese and I may use incorrect English. I’m sorry for that.

First, we usually use “そうじゃないです” or “違います” to deny something, but when you use “そうではないです”, you aren’t completely denying.

彼が唯一の日本人ですか？(Is he the only Japanese?)
そうではないです。(No, not only.)
そうじゃないです。(No, he’s not.)
But I can’t say this is right in any context.

Second, certainly we can’t use “そうです” and “そうじゃないです” when asked in a sentence ending with a verb.

明日来れる？(Can you come tomorrow?)
そうです。(That’s right,)
そうじゃないです。(That’s wrong.)

This is odd. You should say “はい”, “来れます”, “大丈夫です”, “いえ”, “来れません”, “無理です”.

Third, depending on the context, we can’t use “そうです” and “そうじゃないです” when asked in a sentence ending with an adjective.
But this is really complex and not decided strictly.

When A suddenly asks B.

A カナダって広い？(Is Canada large?)
B そうです。(You are right.)
B そうじゃないです。(You are wrong.)

This is odd.
But if you say “そうですね”, it doesn’t sound odd.
Because “そうですね” is also used when you are asked and thinking like “let’s see…”, “そうですね” can be used in various contexts.

When B has told A that Canada is large and A wants B to say yes.

A カナダって広いよね？(Canada is large, right?)
B そうです。(You are right.)
B そうじゃないです。(You are wrong.)

This is OK.
In this context, “そうじゃないです” may express a little anger.

When A wants B to say his opinion.

A その犬は可愛いですね！　(That dog is cute, isn't it?)
B そうです。(That’s right.)
B そうじゃないです。(That’s wrong)

This is odd.
You should say “そうですね” though “そうです” isn’t too bad.
You can’t say “そうじゃないです” because denying someone’s feeling is impossible.
When your the dog is yours, you should say “そんなことないですよ”.
When it’s not yours, “そんな事ないと思います”.