Is a max expatriation not going to be of benefit to China in their move to culturally control HK? Part of me understands the need for a lifeline to those who want out, but part of me also wonders if the UK isn't more than happy to do this for China, who would probably love to have deported them anyway.

Similar to how the US no longer recognising HK as autonomous was framed as a pro HK gesture, but surely that's exactly what China wants. For people to recognize it's control over HK legitimises that control.