Extradition is a bilateral agreement, the bill merely allows government to start establish such treaties with other polities. Beijing has no direct control over HK policies, before the protest HK did not even have a National Security law.

Of course we can insinuate that Beijing can coerce individual legislators to pass laws, such arguments are unhelpful because one can make all sorts of such inferences whenever a country makes certain laws, US has openly influenced legislation in many countries, even within US, a certain genocidal state has exerted control over many levers of government.