I suspect the truth is more like, people who are insistent on training their DC at a ridiculously early age, at a year or so, are more likely to risk problems, but even that is by no means certain. 2.6 was certainly earlier than we went for it, but of course some DC are going to be perfectly ready by then, and not in the least damaged by the experience. We gradually started at 2.7/2.8 but with no pressure (just getting the potty out for them to try out), and then did the whole thing very easily when they just turned 3 - since then we've had virtually no accidents, so it worked well for us. But of course you've got to use a bit of common sense to look at how ready your DC are and what feels best for you.
Having said that, we live in Germany, and it's definitely my feeling that parents in the UK are keen on training a few months earlier, and more proactively, than German parents.
We DO have an example of friends who managed to psychologically really damage their DD by pushing training too early. This was a Spanish friend who was put under extreme pressure by her own mother to train from a year onwards and used being dry as a measure of parental success. This friend kept on asking us in our group of friends 'so, is your DD dry yet?', and we all replied, 'er no, we're not even thinking about it yet'. They persisted with the training regardless, and then by the time their DD was 5 she was shitting everywhere apart from on the toilet, presumably because she associated it with stress and misery. She got sent to a child psychologist who spent ages trying to 'deprogramme' her from that way of thinking. But her situation was extreme.
The article is the typical Daily Fail, er, shit. Ignore.