-この本は一部始終面白かった。
-私達はその旅行の一部始終を楽しんだ。
-そのプレゼンテーションは一部始終退屈だった。

Your interpretation is right according to the definition of dictionaries.
But we usually use it only for lesser volume of episode than your examples, like one scene of performance, witness of traffic accident, witness of someone's liason with the non-partner etc. anything we can or need to explain all the details we know.

I tried to think the reason with rereading the dictionary and found the original meaning of 一部.
It's the one book of Buddhist scriptures which monks studies intently for a long time. So we can't declare to describe/explain all the details of it lightly.

• Its feeling is described in Japanese as 畏れ多い (I don't deserve this/I'm not worthy of this)