You say baby backs, at 300°F, baby backs, especially the standard thickness ones can be done in 2 hours or so. Depending on how he is measuring, he could easily be at 325F, which, even that 25°F difference can be a big difference in time.
To answer the question of why the hurry, surely, it isn't always necessary to cook hotter and such. But, at times, you just don't have time, and really want ribs, or you have mistimed other things, and need to get things done. To some degree, the more tools and experience you have, the better the cook you are when things go wrong.
As for meat drying out, that is not so much a fact, there is evidence that there is a happy medium. Some classically trained cooks believe very strongly that for most cuts, hotter is better.
the meat thermometer was so far past the top reading, it read Taylor
"perhaps...but then again...maybe not..."