At the school I went to, and several others I know of, the thing a PhD writes was called a thesis. In practice, the two terms seem to be used interchangeably. There might officially be a distinction, but it’s not made in speech by most of the relevant folks.
We interchanged the term too. Mostly we called it “thecal material”
I thought Th.D. stood for “Doctor of Thinkology.”
Anyway, I have been on search committees for faculty hiring in a university engineering department, and we always contact the candidate’s alma mater for official verification of degree. I don’t suppose it’s something you could do in the middle of the night for booze-fueled fun, but it is normal practice between academic institutions.
IIRC my only guidance re: length of my dissertation was “not overly long.”
And the guidance I got was “as long as it needs to be”. Some, like DeBroglie’s, are much shorter and quicker to write than others, but even for its shortness, it still managed to present and develop a significant and original (in fact, revolutionary) idea.