As the Messages RCS implementation is supposedly E2EE from device to device; No. It is not possible that a log of your messages' contents are being kept.

Can it stop them from storing your encrypted messages to decrypt later if law enforcement should be able to confiscate your phone and extract the encryption key? Also No. It is not possible for E2EE to prevent "Store ciphertext and decrypt later" attacks.

It also cannot prevent companies from logging who you are conducting an encrypted conversation with; even if the contents cannot be seen and this information cannot be used to infer anything about the contents. It cannot stop companies from making inferences about your messaging activity due to timing of messages sent or who they are sent to.

If these kinds of attacks are on your threat model; you need to ensure you are not sending messages or information via electronic means via your phone to begin with, wherever possible.

It is absurd to assume that they have backdoored the RCS protocol without proof or evidence. This isn't saying it's a verifiably secure or private protocol; but I think you could trust an E2EE RCS message for long enough to help you get someone else onboarded on to Signal or another more properly encrypted messenger without needing to worry about being put on a watch list. I would trust it with my grocery list or trivial communications with family; even if I wouldn't trust it with my truly personal or private conversations.