A cover layer is there to show how you fit the role. This cannot be done with a genetic cover layer

Telling facts about yourself is done in the CV, not cover layer

Sure, but the parent was talking about customized resumes, not cover letters. The cover letter of course needs to be customized, else it serves no purpose.

This does not match my experience. Most of the time it's quite clear who is a high performer/multiplier in a team

At the resume stage?

At the interview stage

Missing the point by a large margin...