If you're a "short and fat" engineer, and you know it, it's very hard to stay that way, and also stay in engineering. Either you become a T-shaped engineer, or you move out of engineering to apply your broad-but-shallow knowledge in ways that elevate others (e.g. PM work).

"Short and fat" is a transitionary state. Staying there is just logistically hard, not to mention handicapping in situations where being deeper in one specific area would help.