Companies can add or take away rungs on the ladder, but the number of rungs doesn’t really matter. What EM calls 6 promotions to get from CL 22 to CL 28, maybe Joe Oil breaks into 18 promotions, so he gives 3 tiny promotions in terms of salary and competitive skill sets vs 1 for EM. Maybe more but smaller promotions make some people happier, but in the end it makes no difference. I suspect his workforce would complain that their promotions aren’t anywhere nearly as large as EM’s, so there you go, can’t win.
Most companies layout skills, accomplishments, knowledge, breadth and depth of experience, recognition among industry peers, etc. that they feel a “fully qualified professional” would attain, and assign a CL to that. For EM, let’s say that is CL 28. They then create a series of steps or levels to measure progress against those and break these into different CLs which culminate at CL 28. It’s that simple and arbitrary. Like mentioned below, CLs don’t mean much in terms of salary, as a highly ranked CL 25 can make more than a poorly ranked CL 27. Many, many people stay at a given CL for years and years as they approach either their final potential or the qualifications for that next CL.