I did not know that, though I do recall hearing stuff about portable numbers etc. Do you have a link for that, by chance?
Quick Google, there was a thread on it here a while back. Seems to be just new numbers? But I expect they may have included prepays since https://www.france24.com/en/20191201-china-introduces-mandatory-face-scans-for-new-mobile-users-raising-surveillance-fears https://edition.cnn.com/2019/12/02/tech/china-facial-recognition-mobile-intl-hnk-scli/index.html
And because the scared public in the UK atleast are well scared, they've signed away a lot of rights and will be heading that way soon
Not only is it not odd, it's completely expected. It would have been odd if subscriptions had not have been lost. The reason is simple: economic downturn - business slowdown / reduced consumer confidence; many housebound (with wifi) during lockdown, so less need for cell phones. What happened in 2008/2009?