The first thing which comes to mind when I hear competency based education (CBE) is a policy of mastery, specifically a redo policy which is designed to work toward equivalent outcomes, essentially obscuring differences in speed of learning. This may benefit lower performers.

Another thing which comes to mind when I hear CBE is a policy for granting credit for learning experiences outside of the classroom or specific institution, designed to avoid repetition. For example, colleges which grant credit for certain types of work experience, or high schools which accept outside coursework. This may benefit advanced performers.

The link upthread about the Royal College of medicine states, in part: "from residency through to retirement... more emphasis is placed on regular assessment of performance... after certification and throughout a physician's practice" which seems to echo the ACT workforce plan to "Assess your workforce... Validate your workforce... Certify your workforce... Reinvent your workforce", with assessments which evaluate a number of skills, including soft skills such as teamwork, fit, performance, talent. This benefits the testing companies, apparently. It may also provide HR departments (or overseeing governmental bodies and regulatory agencies) with cause for dismissal of an employee who otherwise seems to be contributing in meaningful ways.

The U.S. Department of Education defines Competency Based Learning or Personalized Learning. Wikipedia also discusses competency-based learning.

To gain a clearer picture of what Iowa plans to implement as CBE, I read the 43-page pdf, final version of the task force document found online, which says, in part, "allow students younger than ninth grade to earn credit in any curricular area toward graduation if they complete the requirements for the credit". The document does mention gifted students, specifically gifted students dropping out of high school. Sensitivity to this issue seems like a plus. The document refers to the Iowa Core.

Interestingly, the map of common core adoption by State shows that Iowa has adopted the Common Core, and refers to the Iowa Core... giving the impression that this is part of the implementation of the common core, presented as local control.

From all these things I gather that CBE describes itself as providing more freedom and flexibility (in the short term) while also imposing more assessments and gathering more data, which may impede personal liberty and self-determination (in the long run).