it clearly (enough, kinda) communicated
1. what data they keep/collect
2. what they do with it (and that there is a reason to have it)
3. with whom they share it
4. how long they keep it
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GDPR might require data minimalism, but that doesn't mean you can't keep "all" conversations/data. It just means you have to have a reason of why exactly need all of it (they have), only keep it as long as strictly necessary (they do) and not use it for other purposes (they claim to do that).
Also from a legal POV you can't really argue that collecting all conversations for detecting abuse patterns is "unreasonable"/"unnecessary" or similar, as to some degree the AI Act requires exactly that for "high risk" AIs/use cases. And while by the definition of the AI Act AWS Bedrock likely doesn't fall under "high risk" they can argue that some people could (against TOS) use it for "high risk" or "illegal" AI use cases which is part of the "misuse detection" thing for which they keep conversations for a month.
Lastly GDRP deletion requests still apply. But need to be processed within ... 1 month (wich AFIK in a generic duration context you can treat as 30 days, even through there is a single shorter month). So they "auto comply" with this, too.