I doubt he will use SDL, the author mentions in another video that he is interested in implementing his own render. Also, he claims he won't use DirectX or OpenGL.

He said he might you some OpenGL near the end. Hopefully, he does because using the GPU will allow for so much more performance. I guess he can make that a separate class.

Yeah, because SDL is not an engine, so he can still boast he made it from scratch.