On the 50% reduction it only applies to those with year ends July to September, see the FAQs on that page.
We have automatically applied the reduced threshold to Silver Members with Tier Point Collection Year end dates in July, August and September 2022. If you collect 300 Tier Points by the end of your current Tier Point Collection Year, or fly with us on 25 eligible flights, your Silver status will automatically renew.
Please note, the Tier Point tracker on ba.com will continue to show a threshold of 450 Tier Points as this reduction does not apply to all Members.