Good observation! The living plant synthesizes and releases components of their oils consistent with its biological needs at any given moment in the life cycle. The distilled oil contains many of the same molecules that the fresh flowers emit, but not necessarily in the same quantities. Furthermore, many of the very high volatility components are not recovered during distillation, and some of the least volatile components hardy make it out the the plant material in the still. The scent of the resulting essential oil is therefore similar to but different than the fresh flowers.