I can't remember exactly where I read it and as far as I'm aware, research doesn't have to be official to still be called research. I'm not entirely sure what point you're trying to make here or what pearls of wisdom you're trying to impart.
It does need to follow a proper methodology and be peer-reviewed (checked by other professionals) to be called research.
As you've mentioned there is easy enough evidence to support real life cases
Not that much: a few books written by individual parents (I can think of 2 or 3) about their own families seem to have had an inordinate amount of influence: I could easily come up with as many RL examples of the opposite working.
and if you really need official studies then as you've indicated it is your profession to find these
Yup. They do not appear to exist.
and you also have grown up children
Which is why I am able to claim with some confidence that at least in my case a different method seems to have worked.
and of course to write provocative comments on forums online
What is provocative in asking you if you have evidence of something you claim to know from research? You are in AIBU, yet you seem to think there is something provocative and wrong in people having a different opinion.
therefore I presume you have time to put in the research yourself
I have done so. There does not appear to be any convincing evidence. The OPOL school is a very Western-centred approach which is based on anecdotal data by individual parents rather than any proper study of a large sample of children conducted by professionals in data collection and analysis. In the meantime, outside Western Europe and the US, people manage multilingualism in all sorts of ways and do so very successfully.