Is O(n + log n) really a thing or should he just write O(n)?
Long answer is yes because O notation is commonly written this way to be more illustrative of what’s happening in an algorithm and that were smushing to algorithms together.
If you can be more precise then feel free to write it down. For example O notation hides a constant factor but if you happen to actually know it exactly you might see O(7n) in the wild.
Thanks for catching the mistake, @dmurray. I'll fix that.