That was my first thought, too. It seems quite plausible that the exact skills suited to doing well in sales (competitiveness, focus on short-term gains, etc.) may be the exact opposite of skills suited for managing.
The article's generalization from a specific employee type to all employees is unfounded.
It's universal across organisations: you need people management skills to be a manager, while most other positions require skills specific to their domain such as being a good confidence artist to make sales, being a good logical abstract thinker to be a programmer, and so forth.
Generally speaking, promoting someone who has great technical competence into a soft skills position is a recipe for disaster: you lose both a good manger and a good technical specialist.
The fundamental flaw is perceiving management as a senior role, when management is actually a subservient role to the rest of the organisation.
To go this route you'd need to delegate substantial decision making power for technical questions. Most companies don't do that, and plan to have unicorn managers with both skill sets.
The ratio of tech to people skills depends on the difficulty of execution. In the 90s when every tech company was a "hard tech" company you needed technical representation at a high level. Bill Gates would only allow former programmers to manage his programmers for this reason.
The article's generalization from a specific employee type to all employees is unfounded.