From which point on does the 70% rule apply? Is it for 2021 proposals that will be submitted in 2022 or only starting 2022 call for 2023 resubmission?

The resubmission 70% rule applies as of 2021 proposals and re-submission in 2022. The conditions for MSCA-PF as stated on page 83-91 of the MSCA Work Programme 2021-2022 apply to both 2021 and 2022 calls, so it means that 2021 proposals cannot be resubmitted in 2022 and 2022 proposals cannot be resubmitted in 2023. Quoting page 85: “Proposals involving the same recruiting organisation (and for Global Postdoctoral Fellowships also the associated partner hosting the outgoing phase) and individual researcher submitted to the previous call of MSCA Postdoctoral Fellowships under Horizon Europe and having received a score of less than 70% must not be resubmitted the following year.” It means also that the researcher can (re)submit the proposal with a different host, so they are not totally banned from applying the following year.