My spin on it:
The main purpose of a tiddler is that its content can be reused in another context. There is little reason to split content into parts that are not intended to be apart - including the bible for that matter, if it is to be used as a complete start-to-end unit. But then, it is probably too big to be a TW for technical reasons.
Conversely, if the smallest fraction is intended to be used in another context, well then there is reason to split it off into a tiddler.
Sure, there can be other arguments for splitting up tiddlers (e.g aesthetical, memory management, etc) but that is not why TW exists, it’s *raison d’etre *. The uniqueness of TW is how it enables weaving information into different stories. This is what the TW “tools” are about.
Tiddler philosophy formulates tiddlers as the “smallest semantically meaningful units”. I don’t think “semantically” is the correct term here because it focusses on some linguistic aspect, and I’d rather see this formulated as “smallest contextually meaningful units”.
This is why the best advice to beginners who “worry” where to split texts probably is “Don’t worry. Make a guess, or even don’t guess and leave it big and then split it when the need arises.”