Full article from The Points Guy UK claiming that for existing Silver members only, renewing Silver will only require 300 points. For those (including myself) trying to make Silver from Bronze or Blue, the threshold remains 450 tier points until the end of December 2022:
https://thepointsguy.co.uk/news/british-airways-reduces-silver-status-requirements-300-tier-points/
I couldn’t find any confirmation on BA.com.