Is SASI index in Cassandra efficient for high cardinality columns?

[Kant Kodali]

I understand Secondary Indexes in general are inefficient on high
cardinality columns but since SASI is built from scratch I wonder if the
same argument applies there? If not, Why? Because I believe primary keys in
Cassandra are indeed indexed and since Primary key is supposed to be the
column with highest cardinality why not do the same for secondary indexes?