I think you can both be right, somewhat.
The author supposed the person with 50k hours will be better than the person with 500 hours, but maybe just 5x better not 100x better. And that could be accurate. Put each of them in 1000 identical situations, and the more experienced one will close more deals but not 100x deals, probably.
However, that's not the real world. In the real world, the salesperson with 24 years of experience has contacts and relationships that, to your point, will help them land more lucrative deals. So, yeah, they might not close 100x the number of deals, but they could easily close deals worth 100x to their business.
Or to frame it in software development, if you give the same exact task to a developer with 12 weeks of experience and one with 24 years of experience, the more experienced one probably won't finish it 100x faster. However, if you're giving them the same tasks, that's a gross misuse of skills. The more experienced one might architect the system so that task naturally falls out of the design or knows of an open source tool that can handle it with no custom development or maybe they understand the business well enough to propose a simple tweak to business processes to obviate the need to do the task at all – that is, they might bring 100x value overall.
My point is just that, sure, there are diminishing returns on experience solving the exact same problem, but a person with 500 hours of experience and on with 50k hours of experience shouldn't be working on the exact same problems.
It's kind of like that old question when looking at a résumé: Do they have 10 years of experience or 1 year of experience repeated 10 times?