From my days in research it's very common to get an email asking your opinion, or if you have any unpublished data, even if you can send your cell line, new drug, or whatever to another lab.
Usually you know the asker, or their lab/professor, so it's no big deal. I've sent all sorts of stuff all over the world.
You're not expected to fly to their lab and physically help/input into their research though.
If you get such an email off a lay person or member of the public, you politely decline to help, or pass it on to your pr office if they are a bit weird persistent.
It may be dr hirano simply thought he was giving an informal opinion, especially as charlie wasn't his patient and he isn't licensed to practice in the uk. Gosh were in the process of applying for permission, so maybe it was "hey mate, if we get approval can we have some of your nucleoside stuff". Which would explain why he'd never considered charlie a patient or looked at his medical history.
The mistake was "the letter". But again, c&c were/are insisting no brain damage so maybe they were misled. Do we even know who was on it? I was under the impression it came from the italians, maybe dr h wasn't a signatory?
But huge props to judge francis. He played a blinder there, the parents get to make the decision, and a huge mess forcing withdrawal is avoided.