Primary Key Type's Effect on Performance in Oracle?
From what I know, it depends on whether your table is IOT (Microsoft calls it clustered table, a table with clustered index)or not . Historically, Oracle IOTs performed worse than its heap tables. That seems to change (I believe with Oracle 10), but there is still prejudice against IOT. So the article you mentioned can be applied to some extent if you use IOT in Oracle, but not for heap tables.
Don't misunderstand me, having a PK constraint supported by index on large varchar2 column has impact on performance, but if it's an Oracle heap table, it's the same as having an index on non-PK varchar2 column.