I think you're asking whether a proper professional with adoption related expertise will have helped in the training materials used for training adopters? OK well this is the long answer (actually it isn;t - there's a longer answer but it's late and I've driven to BRighton and back today already)
Yes - training is generally (I can't speak for every authority but I know the London authorities appear to work together on areas like training to keep standards high) prepared with the input of various professionals with expertise in adoption-related research and therapy eg there was a pan-London seminar this year (probably the largest ever of its kind in the UK) which focused on supporting LAC's and previously LAC's in education and the audience comprised of social workers, educators, adoptive parents and a handful of foster carers. The content extensively referred to evidence-based research that has been done in various areas including psychology and neurology and talked about the research into brain development and how to form new neural pathways and cement them.
Likewise my prep course (although some years ago now) which although it was predominantly focused on the practical - likely issues which crop up, role playing various scenarios like discussing difficult life stories with your child, tackling racism and adoption bullying, also included extensive reading lists and made use of studies - some quite old now like the groundbreaking Bowlby work on attachment to the relatively newer discussions on brain plasticity which is obviously of great relevance to adoption and the "mindful emotion coaching" approach to parenting and education and the "attachment friendly schools" initiatives. (Bath Spa are doing a lot of work in this area)
Not all of the "experts" who have input are psychologists, some are educators, social workers, psychiatrists and other therapists. Though most of the research they base their work on is by psychologists such as Dr John Gottman (who has done heaps of research over the past 30 years on raising happy children not adoption specific).
So from my experience, all of the training I've done has been rooted in solid evidence-based psychology even if the training is presented by social workers. There is a strong preference in the UK for evidence-based research so there tends to be a reluctance to follow the latest theory unless it is backed by good research - so its possible that some of the very newest theories are not covered but in my opinion in the absence of evidence thats probably right. But as I say I can only speak for the training over the years that I've done not for all training across the UK. To a degree also, after the prep course how well trained/read you are is pretty much self-driven though in my experience the majority of adopters are knowledge hungry and you often see people swapping book recommendations and sharing articles on here.
As for actual therapy in practice on the ground, in my personal experience is that any practitioner experienced in adoption (in any field) is as scarce as hens teeth even if you are prepared and can afford to pay.
In DS's case - initial contact with post adoption support...
adoption team "well we suggest from your description of the problem he might have XYZ issue (they were right btw!), ummm... tell the school to sort it out"
school "we don't have a clue how to access support, have you spoken to adoption? Yes? Oh dear - how about play therapy?"
Me "Hmmm, I'm not convinced play therapy will cut it but what the hell I'll try anything at this point"
Play therapist "sorry I'm not trained to deal with adoption issues"
Me to school "have you tried Family Futures?"
Family futures "No we don't offer individual therapy in these situations (he isn't bad enough) but these are the training days we do for teachers"
Me "OK I think he has anxiety issues and EPD and I'd like him assessed by the EP"
EP "If I think any of his issues are attachment related I will have to pass as I'm not trained to deal with them"
EP "OK you are right he probably doesn't have any attachment issues (or not significant) he definitely has severe executive processing problems but other problems (left out for DS's privacy!) means that its hard to use CBT on him (they tried for 8 weeks) - how about I review him again in a year or so, I'm not sure what else to suggest. Bye"
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Btw, I don't have a stand off - I just don't agree with some of what you say and you don't like my posting style (or maybe you don't like me posting at all!)