He deserves a lot of credit. There are a couple things I'd say though:
1. I think people are realizing there's not that much of a talent gap between Purdy and Jones. Part of the reason you bring in Jones is for this reason. And we've pretty much always known that Shanahan's offense is largely QB-friendly.
2. Something people have been saying since the preseason, but they have an extremely friendly schedule this year. NFC South, AFC South (played the Colts with Rivers, not Jones) and Giants/Browns. You can lose all four to LAR and SEA and still win 9-10 games with that schedule easily.
They're a good football team and a contender. But keep in mind that, today, they're 9-1 against teams .500 or worse (only loss to Tampa), and 3-3 against teams +.500