I think it's alright.

It conveys what needs to be conveyed in an approachable way. It could be more accurate and/or precise, but it shares this quality with a lot of other explanations of technical things that are written for broad audiences. I'm inclined to give some slack to a journalist from Kosovo who probably did not learn English as their first language.

If I were editing it then I'd consider replacing the word "data" with "information," to encompass the entire gamut. But it is not particularly egregious as-presented.

> If someone reads this quickly, they might easily conclude that data is also transmitted as analogue sound signals (like a POTS modem) when ADSL has been around for many years and has pretty high throughput.

If someone were to reach that conclusion, then it would be a valid conclusion.

Data may come out as 1s and 0s (or digital words or frames or whatevers) after demodulation at either end, but on the copper wire between those endpoints ADSL is absolutely an analog signalling system. That's what it is designed to be.