grammar - Can "so" (as a conjunction) be followed by a sentence the subject of which is omitted?

Recently I have come across this strange sentence:

The paper was mainly about the everyday life of the ordinary people during the Japanese occupation so did not favour any student of History.

Can we omit the subject after the conjunction " so" when it is the same as that of the main clause? If we can, then what about other conjunctions like "as" (in the sense of "because"), "because", "since"?

I know the omission of subjects is common for conjunctions like "if", "when" and "as". But rarely do I see this happen to conjunctions showing casual relationships like "so" and "because".

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