Apparently since 1984, when he won a prize for writing a computer game at 12 years old: https://blastar-1984.appspot.com/
Unless you present your engineering qualifications that are of equivalent credibility as that of the aforementioned people, as well as present evidence that you've worked with him as closely with Elon Musk as some of these folks have, I'll stick with my conclusion that, yes, he's indubitably an engineer.
[0]: https://youtu.be/PlLmdTcsAWU?t=1439
[1]: https://twitter.com/ID_AA_Carmack/status/1038832124747571200...
[2]: https://www.youtube.com/watch?v=GNG6ZzDh9C8&t=390s, https://www.usatoday.com/story/news/nation/2020/05/26/spacex...
[3] https://twitter.com/lexfridman/status/1225875212559933442?la...