I like what you say, but thought I should add my own thoughts from a more contemporary UK background too, as it is plain a lot of older adopted people haven't quite appreciated how far the system has evolved. Yes, it could evolve more, not saying it doesn't need to! And yes, I appreciate even with these reforms there is still an ambivalance on the part of some adoptees about their status.
Firstly, nowadays the only legal link with your parent once you turn 18 is that of presumed 'next of kin' should you die or need powers of attorney, at least until you have children of your own. This is the case for *everyone* nowadays. Some adopted people change this back to be their birth parents in a Will (should the birth parents consent to). This effectively ends the adoption. Yes there is no state-bestowed piece of paper confirming that, but you have severed the only legal link with your adopted parents, and what's more you are in control of doing that. I'm not sure what the point of having a certificate to enshrine that would be, as your adoption is still part of your history, you can't erase it as much as you might like to.
Secondly, adopters are already classed as guardians/carers for an indefinite period of time at the start of the placement. They have no control over when, or even if, an Adoption Order is granted, that is entirely down to the whims of social services who nowadays are in no rush to push it through. In my own case I was a guardian for only 13 months, but I've met people for who it was 3 years and have heard of 5 years. A guardianship cannot be obligatory on the guardian (they can step down), as that would violate their own human rights because they are not the parents. So therefore, just like foster care, it isn't considered permanent. And some kids need permanency, so when that happens the guardianship is turned into an adoption.
A guardianship also means that the birth parents retain some parental rights, but none of the responsibility. That is not usually a desirable situation which is why usually it is only family members who become special guardians (i.e. until 18). There are twice the number of special guardianships issued as adoptions.
Thirdly - an adopted person no longer has a 'new' identity, if they ever actually did. The only thing that changes is their NHS number, as AFAIK it used to be the only way they could ensure the NHS's antiquated IT systems could cope with the fact that someone else now had parental rights for the child. There is no new birth certificate. That's a hoary old myth which may have had some truth a couple of hundred years ago, but trust me, isn't true today. I just applied for my son's passport by coincidence, and had to tell them all his 'old' identity info too.
Fourthly (sorry, spouting on here), all adopted children will know their family history, and it is now an obligation on adopters to keep them in touch (in person I mean) with anyone they had a significant safe relationship with prior to being adopted. Usually that means siblings.
