Fixed in master and 5.0 branches.

This jira covers the case where Hibernate "knows" that the Java type of attribute with an AttributeConverter is immutable, for example:

{{// Hibernate knows that Integer is immutable;
@Converter(converter=ValueTypeConverter.class
Integer aValue;}}

HHH-10127 will cover the case where an application can explicitly indicate that the Java type of attribute with an AttributeConverter is immutable, for example:

{{// Hibernate has no way of knowing if ValueType is immutable
@Converter(converter=ValueTypeConverter.class
ValueType aValue;}}