Why does a SELECT query (Sch-S) get blocked due to an existing Sch-S lock held by index reorganize command?

SELECT query requires a SCH-S lock. This can be shared with other read queries. UPDATE query requires a SCH-M lock. This cannot be shared with other read/update queries. Link: https://www.mssqltips.com/sqlservertip/5880/why-is-index-reorganize-and-update-statistics-causing-sql-server-blocking/ The example shows an index reorg (Sch-S) lock blocks the statistics update's Sch-M lock. But why does it also block the subsequent Sch-S lock requested by the SELECT query? Aren't Sch-S locks shared?