What is incorrect exactly? Is it incorrect to say that an Epson or a Plustek don't have the same DR as a higher end scanner like a Flextight?
Don't twist what you wrote. You wrote the following
Do not try to achieve a perfect image directly via the scanner, they simply do not have the dynamic range to cope with a typical well exposed negative
You made a blanket, incorrect statement about 'scanners' in general not about 'Epsons' or 'Plusteks'.
The dynamic range of the CCD of even a medium range Epson flatbed exceeds that of film. That is not surprising, because if I were an engineer working to design a popular, mass produced scanner and I worked for a well resourced Japanese corporation, I would do some research into film latitude before deciding on cost/benefit ratio and price point of the CCD line sensor I'd recommend to adopt for the scanner design.
The range of density on color negative film is approximately 5 stops. That of reversal film and B&W film is approximately 7 stops. The CCDs in many consumer scanners have a range of approximately 9 stops.
The issue of DR in a B&W negative (given the sub-forum where this thread is posted I'm assuming OP is interested in B&W negatives) is a non-issue when it comes to scanning, because, as you probably know, the negative is a non-linear information storage device as Zones I-III and Zones VIII-X are compressed wrt the reproduced scene. They are later to be expanded via projection on photographic paper or suitable re-linearisations done at scanning time.
As other commenters are correctly suggesting, the device is likely not the culprit here.