Btw, from what I can recall, even within education system, we always pronounce tone three the low-and-flat way, the drop-and-rise is rarely heard of.
I guess that's why I didn't get your question at first.

In normal conversation, the way we pronounce tone three would sound low and flat for the sake of fluidity.
Perposely speaking the "formal" way will makes you sound either too stiff or too dramatic.

It really is just to smooth out the pronunciation so the sentence doesn't sound "chopped up" and stiff, I'd say there's no rhyme or reason behind any of those.
Emphasizing? Sometimes yes, sometimes no, contexts matter.