The issue is:
The broker I run (2.7.0) does not accept a DescribeUserScramCredentials request with compact array
The response I receive always contains all the users (even when requesting for a specific one)
The response I receive has some extra bytes which do not follow the schema posted on the Kafka protocol website however it does look like it uses compact strings and arrays.
Please read the discussion in the imgur. I can't write it here since I am writing it from my phone.
I will throw this here, an issue I have been working on alongside the devs of kafkajs. I would love for more insight in this.
Our entire discussion and my conclusion: https://imgur.com/a/iHaKwH8