Even when you study 5+ years in Computer Science & then work 12+ years in Software Industry, you'll not know everything. But if you are even a least bit curious, then you may find yourself in a position where it's hard to introduce yourself as an expert in a single field.
Full Stack doesn't mean you know it all. To me Full Stack is an idea, it shows passion, curiosity and completeness. Most of what you know today will be completely obsolete in the next 10 years. Full Stack means that doesn't matter to you, you can fit right into 99% of the software development scenario within 2 weeks. Full Stack means you are ready for the next level, to be the project manager - to be in the top of the food chain; but at the same time, you'll be able to get your hands dirty with CODE when it's needed or perhaps purely out of the fun of it.
Don't get me wrong, your suggestion has merits, it just doesn't fit into every scenario.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.