He appears to be tunnel-visioning on academia.
The vast majority (>75%) of Computer Science PhDs leave academia. [0] Becoming a "world expert in a specific topic" is overfitting skills for a sub-niche of a specific career. There certainly aren't enough jobs in academia.
[0] https://academia.stackexchange.com/questions/213640/what-rat...
You’re arguing that we have too many PhD students in CS, not too few.
I agree with you fwiw.
The goal of a PhD is to become a world expert in a specific topic, whether or not you’re planning on staying in academia.
This may or may not be in alignment with the student’s goals, and many students don’t really understand it going in.