There isn't necessarily a USB standard to compare with to that end, as type C supports a wide range of standards. Compared to lightning, both iPhone 14 and 15 seem to offer up to 20W charging with the wall adapter sold separately. So again, no improvement where it could most likely be provided easily (e.g. like any other phone manufacturer has), but charging rate isn't solely determined by the port/cable in the same way as data, there's ample room for Apple to argue that the charging is slower on the base model for some other reason related to production cost vs. Pro