He probably also wants to push Harry away from new spells for safety reasons (presumably he thinks Harry might try to science up a dangerous new spell and that's how he ends the world; he has some experience with Harry attempting to combine magic and science from Azkaban). If he personally steers Harry towards old spells then at least he knows what those spells do.

It's also possible that the Restricted Section contains enough information for someone like Harry to figure out how to create spells from reading it.