The DT Swiss chart, is much more in line with current rim and tire design than the "ETRTO Chart". The latter was based on tires and rims from the late 70s/early 80s and is overly cautious and not applicable to modern systems as well as being based on a standard that no one has ever seen and is not freely available to review.

I will add the DT Swiss chart is also a overly limited. I rode and raced 55mm tires on 17mm inside width rims for a couple hundred hours and am currently riding 32mm tires on 25mm inside width rims with no issues.

The best thing to do is run whatever tire width you want and make sure you accurately measure the tire width on the rim and use that to set proper tire pressure and sag. The charts are to protect against things like excessive casing tension and pressure due to a narrower nominal width tire being mounted on a much wider rim. If a user mounts a 23mm tire on a 25mm inside width rim the tire is most likely going to be between 25mm-28mm wide actual and will have a reduced ideal and maximum pressure compared to the nominal design width. Converse is also true, wide tire on narrow rim will be narrower and require higher pressure to prevent sidewall collapse and excessive potential to pinch flat.