Most likely, at that point in time, it is changing beyond the sensitivity of your hydrometer reading error measurement. (decaying exponential). For all intents and purposes probably 98/99% of the fermentables are consumed. The question becomes, is this negligible on the outcome? In terms of gravity I'd say so, but in terms of anything noticeable I'd say this part:
" Also, the yeast clean up some of the byproducts they produced during the fast-paced primary phase."
would have more of an impact on overall beer health. It's all splitting hairs though, and like I said without a way to actually measure these things we won't know, which is why I say it's done by "feel".