Well it only needs to be Kafka-compatible, so personally I hope that things like RedPanda will turn out to be easier to run for this use case than actual Kafka.
Having an S3-compatible store was already a fairly heavy dependency in terms of something to run correctly in production, it's just that most people don't even consider running their own object store at any real scale, they just go to cloud. Whereas running your own Kafka is something more platform teams are already attempting.
"However, this architecture is set to be deprecated in a future release."
So it doesn't stay optional unfortunately. It quite a heavy dependency to include...