But that is really hard to understand for a non-specialist. Means nothing at all for me.

Well, I'm quite sorry to hear that, but the paper was written for specialists, and its results are primarily interpretable by and relevant to specialists. Why exactly it made it into a press release and news articles is completely inexplicable when analyzed within the bounds of the work.

A popular science, or even general news type reviews of current research are very valuable. However, in the unavoidable simplifications, they do need to keep the main findings correct, not expand into outlandish claims for clickbait

I think the fact that the subjects suffer from Progeria (a syndrome that causes early ageing) is significant. There are other effects of ageing (such as damage to DNA in mitochondria from oxidative stress reducing a cell's ability to generate energy) that may not be displayed early alongside other symptoms of progeria and that this treatment would not do anything to alleviate.