Also, the article doesn't mention that native speakers (especially ones born recently) are often able to speak or read some part of the 'other' language. It's a similar situation to French Swiss knowing some German and vice-versa.
I am a native speaker(not born recently though). it still hard to speak or listen 'other' dialect, but more and more Mainland Chinese Speak mandarin instead of dialect， so it's more and more easy to communication.