Why SDL_RenderPresent and not SDL_GL_SwapBuffeon the iPhone?

Hi friends!

Why SDL_RenderPresent and not SDL_GL_SwapBuffers on the iPhone?
If I use SDL_GL_SwapBuffers on the iPhone it does not work, but SDL_RenderPresent works.
If I use SDL_RenderPresent on my Windows PC it does not work, but SDL_GL_SwapBuffers works.

Why?

Thanks a lot.