While debugging the org.hibernate.jpa.spi.AbstractEntityManagerImpl#setLockOptions method call I can see that:

Object lockScope = props.get( AvailableSettings.LOCK_SCOPE );

is properly set to "EXTENDED" and therefore the scope is set on options:

options.setScope( true );

So the option is not taken into consideration somewhere further down the lock method chain.

org.hibernate.jpa.spi.AbstractEntityManagerImpl#setLockOptions