It could be an action from a rogue employee. Possibly not a management decision or specific company policy, just a filter added by an employee with access to it. There might be some 'lively' discussion internally in Google right now over this specific issue. In the past some Google employees have taken actions against individuals based on their personal political beliefs or other personal grudges. A good example of that was when Jordan Peterson was temporarily locked out of all Google services, including his Gmail, insiders said it sparked a lot of internal arguments at the company (eventually his accounts were reinstated with no official explanation or apology, though some employees did apologize to him privately for their coworkers behavior).

It's likely at its core a problem with poor employee screening, insufficient training and supervision, and vague/over-reaching policies given to employees that they sometimes interpret as legitimizing them to censor or ban based on their personal political beliefs.

Some employee there likely is a communist sympathizer, or has other connections to China's authoritarian ruling party.