PreDestroy interceptor method and transactional context

[Himai Minh]

Refer to p.76 of JSR 318, why PreDestroy lifecyle callback interceptor methods for stateless/stateful bean execute in an unspecified transactional context while the PreDestroy method for singleton execute in a transactional context determined by the bean's transaction management type (container/bean managed) and transaction attribute( REQUIRE, REQUIRE_NEW, NEVER and etc) ?