MSK Serverless max message size extendable beyond 8MB?

I noticed that the max message size supported on MSK serverless was noted as 8MB, according to the official AWS docs. However, online, I did see that using the properties of Kafka, this limit (typically 1MB otherwise) can be extended: https://stackoverflow.com/questions/21020347/how-can-i-send-large-messages-with-kafka-over-15mb.
Does the same properties override apply for Kafka under MSK serverless, or is a hard limit set by AWS internally (and I'll need to consider creating a support case for messages beyond 8MB)?

Thanks.