This is true for Postgresql sequences too.
The schema generator ignores the schema attribute of the @SequenceGenerator annotation so that the sequence gets generated in the default schema 'public'.

Example:
For:

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ACR_SEQ")
@SequenceGenerator(schema = "ACR", name = "ACR_SEQ", sequenceName = "ACR_SEQ", allocationSize = 1)
@Column(name = "ID", updatable = false, nullable = false)
protected long id;

The sequence "ACR_SEQ" gets created in the Postgresql default schema 'public'.