应该是按照苹果的订阅规则,为了保证能提前 30 天通知用户涨价,要给老用户按老价格续订一次的机会
[The timing of price consent requests from Apple depends on the length of the subscription. If a price increase occurs within the minimum required notice period (7 days for weekly subscriptions, 27 days for 1 month subscriptions, and 30 days for subscription durations longer than 1 month), subscribers will renew at their existing price for one more billing period](
https://developer.apple.com/help/app-store-connect/manage-subscriptions/manage-pricing-for-auto-renewable-subscriptions/)