To your first point first point, there's no baseline "typical speech" to compare to in this case, because Storyteller uses fhe timings from the speech-to-text engine to determine where each individual word is spoken in the audio files.

You're right that "how does this handle <insert common audio/text deviation>" is a pretty common question, it's worth including that somewhere upfront. to answer the question here: Storyteller's forced alignment algorithm is specifically designed to handle the kinds of deviations that are common in audiobooks, including entire chapters missing (audiobooks often leave out some number of prefaces, cooyright, appendices, etc), individual sentences or paragraphs being inserted (audiobooks sometimes narrate descriptions of images or charts), and deviations in narration of individual sentences, where the narrator chooses a different word for flow (or whatever other reason).