"Play what you know!" An actress who has to play a raging serial killer need not be a serial killer herself (it might even be contraproductive in some way... maybe a bit messy on the set). Method acting tells her to get the emotional framework as close as possible to the feelings of a serial-killer - by re-enacting emotions she relates to (remembering the guy, her first boyfriend left her for would be an example).
"Write what you know!" is one piece of advice for authors that is all too often misunderstood as Jason Gots, associate editor of BigThink, points out. Authors must not restrict their prose to retelling their own (very possibly boring) life - they should map their real-life emotional experiences to the world of their fictional characters. Never been to Mars before? Well, you probably visited some decaying neighbourhood in Detroit or Bilbao. I am sure you found some Martians there. You know how your fictional character feels as he leaves mothership. The same is true for science-communication.
Science-communication is not among the greatest strengths of the average scientist. Some do it brilliantly, some barely speak even in 'real life', some try, but shouldn't. It is wrong, to demand that 'every academic should be blogging'.
Science communication is important. The transfer of knowlede is imperative. The lack of good, adequate science communication is one of the reasons why science has a comparatively weak standing in everyday's culture - despite it's omnipresence. It is 'chique' to state with a smirk 'I never understood physics - and always flunked math-tests at school'. In contrast it would be cultural suicide to describe a classical concert as 'loud but I really don't care what that fiddling is all about'.
Without any research to back that up, however, I would presume that the percentage of people, who understand Ohms law (of resistance) and the number of those who understand a musical composition is equally low.
Conventional 'high culture' gives access through emotions, feelings, opinions (making it possible for a wide public to chatter about it) - while it is rather unconventional to have an opinion on Ohms law. That access to the arts, however, is equally incomplete and inadequate at the end. Both, science and the arts, have an additional level of complexity that is not accessible to the layperson. Music is done no justice if it is reduced to mere sentiment.(You might enjoy the german text "Wissenschaft ist keine Kunst")
Real science can not be slapped on the untrained public. It needs real science communicators to translate in a useful way. Science communication consequently has to be done by well-trained science-communicators, while scientists have to get training to 'talk to' those communicators. The journalists in turn will be fit at asking the right questions and then use their 'method-acting' to entertain the public with a meaningful projection of emotions the audience can relate to onto the science they chose to communicate.
Science communication goes wrong if a substitute-emotion is communicated instead. Just as if that method-actress would chose to impersonate her ex-boyfriend instead of transforming her rediscovered feelings for the role of the serial-killer, it is wrong to write about "time-travel and warp-drive" when scientific work on problems with the interpretation of relativistic effects in an neutrino-experiment was the issue (... is anybody still following me?).
"Write what you know", in this context, means for scientists: when they communicate science they should attempt to transfer their very own emotional experiences to the world of the reader. Some are really good at it! "Write what you know" tells the science-journalist to adapt his storytelling power to the scientific story. As a method-actor would do.