Implementing a degenerate dimension with an alphanumeric varchar(30) at the transaction level?
Kimball's guidance touching on performance and space use needs to be taken with a grain of salt when using modern, columnar storage. And for SQL Server data warehouses, fact tables should typically be stored as Clustered Columnstores. Low-cardinality attributes in columnar storage are much cheaper than in uncompressed row stores.

And wide and high-cardinality attributes in columnstores do have a large impact on storage size, but not on query performance, as columns are only fetched and scanned when needed.  You don't have to fetch, cache, and read the whole row.