If a relative clause modifies a noun or a pronoun in a main clause, then we could use relative pronouns such as that, which, who, whom, whose, and relative adjectives such as where, why.
During reading, I find that sometimes people use a non-restrictive relative clause introduced by "which" to give more information about phrases in the main clause, or comment on part of the main clause or the main clause. Please refer to the following examples. So I am wondering whether we should only use non-restrictive clauses introduced by "which" in these situations (i.e. giving more information about phrases in the main clause, commenting on part of the main clause or the main clause).
Example: 1: He likes climbing mountains, which is a good exercise.
("which is a good exercise" gives more information about "climbing mountains")
2: He said that he had never seen her before, which was not true.
("which was not true" is a comment on "he had never seen her before")
3: Tom was late, which surprised me.
("which surprised me" is a comment on "Tom was late")
Please help me. I really need your help. Thank you in advance!