Mostly true but these days we have the case where regardless of capability it is sadly necessary to put a Ln person to do an Ln's job not Ln+k's job (for political reasons). This has the perverse effect of someone at Ln being punished for doing a job above their level if they are not also doing their own job. What this means is you can only get promoted if you are doing the equivalent of two levels of work at a given time but if you were hired from elsewhere you only need to do the target level job.