Why not a similarly brave stance in China? In China Apple claims it "obeys all local laws" except in the UK it wants to be courageous? I guess it's a brave state unless the $$$ are good.
But... Everyone in China has their iCloud backups stored in China and Apple holds the keys to these backups. While Apple cannot read E2E encrypted Messages content, they do upload an unencrypted (but encrypted with keys they control) backup of all of the phones Messages data.
It seems likely China can ask Apple for a backup of a citizen's phone and Apple will comply with that request. Or they have access to these data centers.
https://techcrunch.com/2018/02/25/apple-moves-icloud-encrypt...
Maybe the difference is that Apple feels they may be able to talk the UK out of this idea.
- if there is success in the UK, relevant persons at Apple can make a more compelling argument to push back on China and other governments a lot more
- perhaps apple is still pushing hard on china and using the UK as an example that they're willing to drop a long time strong market over the anti-encryption legislation
I'm not saying either is the case, but there are benign or even positive reads on why apple is more aggressive with the UK
"At least" companies can put up a fight in the UK (or US, see Apple in the San Bernardino case) and they have a reasonable chance they can lobby to block the efforts.
China is tricky and I'm sure after Hong Kong Apple changed their calculus.
However there is a great chance that if they threaten to pull out of the UK that the law won't pass. Even if it does it is good marketing. Who knows what will actually happen if the law comes into effect. The UK market definitely isn't small, for all we know they may back down. Or maybe their reputation is more valuable.