The cables in your walls are designed for a certain maximum current before they start to heat up. This current is limited by your breaker.
Now if you introduce a plug in solar setup your current is limited by your maximum breaker capacity + whatever your solar setup can generate.
So if I'd use the specs from the article and apply it to a normal dutch home situation: 16A breaker, + 800W at 230V, which means ~3.5A = 19.5A max. which is probably still fine for short durations.
But now some genius doesn't read the fine print and hooks up 2 or 3 on the same circuit. There is no electrician that tells him that's dangerous because it's all self installed and he doesn't know any better. And all of a sudden you are up to 26.5A and you got glowing, smoking wires in your walls...