Oblong is a fluid word, like oval. Had this discussion on another thread about whether Biopace chainrings are ovals. They are in the oval family, but they're -- wait for it -- oblong. Kinda squared off elongated lobes. I think the tech term is stadium, or maybe capsule is more descriptive.
An egg in the shell is oval. The hard boiled egg that comes out is usually oblong, slightly squared off at the wider end.
And the well educated and mad genius Edgar Alan Poe wrote about an oblong box. Angles and sides, not oval. Words are fairly fluid and often maddening things.
Oblong is appropriate to describe my Frankenstein noggin. It's oval, sure, but wider at the occipital than the front. High forehead, everything but the spark plugs in my neck. Or alien implants.