[1] If it weren't for his father's potential disapproval, Sung Hae Rang believes, the match might have proved much happier. "If circumstances had been different," she wrote in her memoir, "they could've made a great couple." Instead, no one outside a tiny circle knew they were partners until after his father died and was succeeded by Kim.

[2] Praiseworthy says that if it weren't for me, we might never have trapped Mr. Cut-Eye Higgins, but it was really the other way around.


Above is the two examples of “if it weren’t for ~~”.

The underlined part, shouldn't it be "if it had not been for “, because the situation happened in the past, and the speaker is referring to the past situation, thus making the "if + past perfect; would have " form of sentence?

Michael Swan’s [Practical English Usage], at page 236, article 259, is clearly explaining the “if + past perfect; would + past participle” type of sentence. But it is not mentioning this type of sentence.

What is more confusing is, in the sentence [1], "If circumstances had been different, they could've made a great couple.", the principle is again being used.

Are there any Gurus or members who can make me understand this confusing English usage?

Strictly speaking it should be if it had not been for, and you will find this, too.
But if it weren't for is an accepted fixed expression used in exactly the same contexts.

Thanks, Guru!