They tried honey - admittedly not a lot and the treaty isn't ratified yet. Now they're trying a bit of stick, between the sanctions and the financial services sector and corporates bending European leaders ears they expect to get reluctant acquisescence - just to warn them 'go further and get the Australian treatment'. Johnson can blame the BREXIT lack of growth on China to whip up furvor and act as the fleet of little ships for BNO Hong Kongese - so poking the panda is popular amongst many of his party members despite his family connections to China. The EU realise that China would hurt if they go after them hard, admittedly the EU, particularly Germany and France would hurt as well. Also the 17+1 attempt is failing because of China's closeness to Russian leader Vladimir Putin in recent times has gone down badly with the Baltic states. China has a lot to calibrate for externally and needs to convey Wolf Warrior style nationalism internally. In addition, there maybe a desire to only have the belt and road go as far as the Middle East because of costs, a desire for the Chinese government to de-leverage and uneven project outcomes.