Nah, Yuri says in either the first or second episode that the NPCs have always been in that world, that they're only fillers to make the place seem normal. And how can I be so sure Yuzuru (Otanashi's first name) created that world? It's because i'm almost 100% positive that the NPC that Yuri killed said that the boy who created their world gave his heart to the girl he loved (or something along those lines), and at the end of Angel Beats it's revealed that Yuzuru had given his heart to Kanade.
Everything makes then. I mean it would too coincidental for it to be another person. So you have best me madam. You have my respect.