Your request for your ACME account ID to be placed on the Let's Encrypt ECDSA allowlist has been moved to production. Now when you request a cert from Let's Encrypt with your ECDSA key, the cert will be issued from our ECDSA hierarchy.
Your CSR looks good to me, and as you say your cert is issued by R3, so it's the RSA chain. Looks like maybe the allowlist takes a while to propagate? When did you get that email?
I know this will probably sound obvious, but are you certain that you used the same ACME account to issue your recent certificate that you submitted for the ECDSA allowlist?
Do you know the ACME account URL that you sent for the allowlist and the one that was used for issuance? (Neither are sensitive information for purposes of posting here.)
and the public key SSL Key for it:
-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----