Narrative warfare is real. Be especially careful when it's something that conforms to your priors. The cost for agitprop is now effectively zero.
I think the more important question isn’t whether the prose sounds polished, but whether the situation described is plausible and whether the discussion that follows is useful. People are free to be skeptical; I’m mainly here to hear from those with relevant experience or practical advice.
Being careful about narratives cuts both ways, including being careful not to dismiss difficult stories solely because they’re uncomfortable or well-articulated.
You don't have to leave for China, there are many places for a talented person (Canada's Vector Institute in Toronto, or good universities in Europe). He was comfortable rather than alert, and perhaps (I reall cannot look into someone's head) priorized his research environment highly (many scientists do).
I know a similar case, where a scientist in a similar area left the UK with his family after the Brexit referendum, but before the outcome of the EU-UK agreement. All his UK friends said "it will be a Brexit in name only" but there were cases of anonymous threats to European friends and slashed tires.
The main risks perceived were (1) disruption of the medical supply chain; (2) the announcement of the UK to aspire leaving not just the EU but also the Council of Europe (rejecting the European Court of Human Rights, including the right to see a legal representative); (3) the lack of any document to prove legal residential status (only possible via an app, nothing given in writing); and (4) a physical attack on trips outside London (the nationalist mostly live outside the capital).
It all depends on if you're trying to maximize (1) family safety OR (2) jointly maximize the quality of your research environment AND family safety or (3) only quality of the research environment, at the expense of anything else.
It's not too late to leave. The question to relocate and give up everthing is hard; it is the same question that Jewish familes had to decide in Nazi Germany, and many wrongly thought that because they were "proper, honest" citizens that should have nothing to fear was proven wrong, and the walls of the gas chambers of Auschwitz contain the scratches of their fingernails.
However your friend and his family decides, all the best wishes.