More of a review based upon record at this time last year. Last year at this time, Purdue was also 13-1 and 2-1.
Now, it is a valid statement to say that their OOC wins this year are better than last years (Marquette, Duke, WVU, Gonzaga), but we wont really know that for sure until the end of the season. (For example, the Duke win was huge at the time, but in the end, the Marquette win was probably their best win of the season. Arizona, as of now, is their best win, but Arizona just got boat raced by Stanford and may end up a fringe top 25 team by the end of the season, we wont know till March).
Even then though, it's more of a question of relativity. They were a top 5 team most of last year and are a top 3 team this year at this point in time (AP 1, KP 2, NET 3). So yes, even if they are better, it is really only slightly better. Not trying to be insulting, they absolutely deserve their #1 spot right now, but they pretty much deserved their spot at #1 at this time last year also.
The eye test says yes they are better, but they dominated the Big Ten last year (won by 3 games), and I expect them to do the same this year. So if they are better, there's not alot of room to be "better" achievement-wise.
Don't know if that makes sense or not.