Sure--until he isn't. And that happens north of "senior".

I've had a lot of I-shaped people reporting to and taking direction from me in my career, and I'm not as deep at any one thing as many of them. But I'm deeper at a lot of things than most of those folks, and I can synthesize solutions to more complex problems because of them. Heck, things I learned writing games in my teens still come up on occasion twenty years later.