This paper, at least by my skimming, seems to describe Redshift's historic SERIALIZABLE ISOLATION level, but does not mention Redshift's newer SNAPSHOT ISOLATION capability.
For concurrency scalability, AWS now configures SNAPSHOT ISOLATION by default if you use Redshift Serverless but non-serverless still defaults to SERIALIZABLE ISOLATION.
>>gregw2+(OP)
Yes. I intended to write exactly this at the end of my post, but I managed to word it completely wrongly. The document describes MVCC as it has been in Redshift until about a year ago, when snapshot isolation was introduced.