Your father may have claimed it was very obvious, but nobody else thinks so.
Golb's son idolised his father maybe too much. I wouldn't be committing crimes to defend Sid's stylometry results.
I think the answer to your implied criticisms would be, "it depends"
Further, as others have mentioned, the consensus is overwhelming that Greek was the original language for the pauline epistles, to the point where I can't even find any contradictory views. That's not to say the consensus is correct, but if there is debate, it's not widespread.
Do you know what evidence your dad had for Aramaic being the original language? A search for "aramaic manuscripts of pauline epistles" turns up no results discussing the topic.
They got people off forged confessions, most of the stylometry work they did was in english, against contemporary documents. Diving into the past was more for fun. The corpus is small and subject to the vagueness of time and editing.
I think I've been misunderstood. Aramaic was the earliest text for which people had high confidence in its transcription from whatever lay underneath. We don't have autograph works, we have copies in varying degrees of fidelity across time, space, language and religious schism.
Did he think aramaic was the origin language? Yes. I believe he did. But, its an outsider theory. Whats less outsider is the age of the text variant, and subsequent divergences.