While I would always want to support this method of production, there is little evidence that it makes any significant difference to the properties of the essential oils yielded. Any such crude methods of distillation, will generally not produce such a good oil, as one that has been produced under the controlled conditions of a modern processing plant. There are of course always exceptions to this general rule, for instance plants such as peppermint and rosemary, where carefully controlled local water and steam distillation is preferable to avoid the volatile 'top notes' escaping. Such statements show a complete ignorance of the chemistry of plant extracts, as well as the plant extract processing trade. The best quality essential oils are cold processed.
Steam distillation destroys or reduces many valuable components in essential oils.
Certainly the highly volatile chemicals which play an important part in the therapeutic effects of freshly gathered herbs are substantially reduced by hot distillation. There are only a tiny number of oils which require hot distillation in order to produce naturally derived beneficial chemicals such as azulenes. The perfumery and food flavouring trade are well aware that hot distillation damages delicate chemicals in aromatic extracts. Due to this they are increasingly turning to cold extracted essential oils, in particular carbon dioxide, or molecular extracts. In addition, according to their own doctrine, they should not use the floral absolutes originally produced exclusively for the fragrance trade, but which aromatherapists are constantly requesting from their suppliers.