"Deduplication" of the key-values is part of the specification and it also involves Body of the log record.
Body is of any type (https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/data-model.md#field-body).
any can have a map<string, any> (https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/data-model.md#type-any).
map<string, any> does not allow duplicated keys (https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/data-model.md#type-mapstring-any).

Currently, we're not de-duplicating key-value collections within the log record body.

Here is what we should add

It is important to do it recursively and also make sure that the attribute limits are NOT applied; see: open-telemetry/opentelemetry-specification#4006.

Originally posted by @pellared in #6968 (comment)