Having trained 3 boys, I don't think it's ever a good idea to "go backwards" when you're making progress. Plus, the best thing about summer time, was they could walk around without pants on - made training really fast! Some kids are dry during the day, but still wear a diaper at night for a while. My point was really just that if the pajama pants fit him when he was a year old (and he looks younger than that to me) wearing a diaper, I would expect them to be too small for him to wear when he's two and a half with a diaper.
Gliving noted that sometimes once a baby stretches out and loses the diaper, pants might still fit a year later. (That didn't work for my kids, but everyone is different.) Since DeOrr apparently hadn't yet lost the diaper entirely, and they were pajama pants which he probably slept in while wearing a diaper if he only wore one some of the time, I'm wondering how the pants would have still fit, as he would be a year or so older and taller, but still have the bulk of the diaper. It's kind of a moot point, but was just following it through.