That dosage (taken over a period of several months every day at the same time) helped me get through a period of insomnia last summer, when basically all the other medications failed or had too strong side effects.
Apparently there are two different methodologies for administering Melatonin. One is to use a higher dose(1mg - 3mg) before sleep (~an hour) as a hypnotic. The other is to take a much lower dose, closer to the 0.3mg you suggested, roughly 4 - 6 hours before the desired bed time.
The latter is used for modifying the circadian rhythm , and fixing problems with sleep wake cycles.
I think the primary takeaway from that show was that people should discuss their sleep problems and treatment with a doctor that specializes in sleep. The treatments and science can be somewhat counter intuitive.
[1] https://slatestarcodex.com/2018/07/10/melatonin-much-more-th...
When I look at other papers in this space I do find some adverse responses in hamster nuts when given melatonin injections (but not when it is administered using an implant).
At this point I did not want to research the other claims in the quote anymore. Instead, perhaps I can ask you: Do you know of any solid research that backs these (frankly very strong and contrary to everything else I've read) claims? If not, why did you choose to say this?