TurboTax correctly uses the 2020 tax data and the 2020 AGI for the Recovery Rebate Credit as required by the IRS tax code and the IRS Recovery Rebate Credit worksheet.
Go to this IRS website for information - https://www.irs.gov/newsroom/recovery-rebate-credit-topic-b-eligibility
The eligibility requirements are the same for the Recovery Rebate Credit as they were for the Economic Impact Payments except that the credit eligibility and the credit amount are based on your 2020 tax year information. The Economic Impact Payments were based on your 2018 or 2019 tax year information.