There is nothing that unique about the inline support of other data structures. Many databases have done it in the past e.g Oracle and do so today especially in NoSQL land e.g. MongoDB, Cassandra.
I think Jeff was principally referring to relational dogma that is so prevalent in other SQL database system culture, even though they might implement such types to get a check-box (or not: MSSQL doesn't support arrays, AFAIK) Clearly nested and record tagged structures are popular in other database systems, but in the universe of SQL systems Postgres has always broken rank with tradition with most of its relational brethren (exception, due to similar parentage: Illustra and then Informix) when it came to data types -- for example, the long-standing inclusion of polygons, lines, and points.
