I think that they shouldn't remotely update ebooks, regardless of their content. (For this and other reasons, I don't really like ebooks, and I like to have a printed copy.) (It can make sense to publish errata if there are mistakes (e.g. a word is missing or misspelled, or a number is wrong), but even then you should not automatically remotely update them, and they should keep track of the changes. A public version control system would help in this case.)

I think that the original versions should be preserved, but that they can make modified versions too if they want to do; however, the modified versions should not be called Roald Dahl's original versions, and should not be claimed to be them; they should be something else. (Fortunately, this seems to be what they are doing, in this case, so that is good, but it does not justify remotely updating the ebooks.) (Copyright often makes both such things difficult though if you do not hold the copyright, but copyright is bad and should be abolished, and then you can both preserve original versions and make modified versions.)