I still have my original birth certificate.. It is part of my history and I'm not ashamed of it. I'm not going to ever use it for anything but I think it's important to keep..
Interesting question though about the registry... You see the original birth record for you is still there.. Should some geanealogist in the future look up the children your mother had, there you will be in the record miss-gendered.. If you had kids, before transition, then their birth records too will dead name you for eternity..marriage certificates too.. Not changed.
What the grc did was to generate a new birth certificate in your preferred gender... Its legal, it's binding and it's the only one you can use going forward.. But it didn't replace anything only supercede it.
You are told when you get your grc, that if you ever need a a replacement you have to apply to a special office and not the usual route every one else does.. For if you try to go the usual route, they will not find a record in that name.. They will still find your old name.. This is why, when you apply for a grc you legally sign away your rights to be identified as that person and you agree legally to never assume that identity again. Your not rewriting history, your just changing the future..
This may seem harsh, but if you think about it, it's the only way it could be done.. Every time you had a passport issued, a driving licence or paid tax etc would have to be retrospectively changed, kids birth certificates, directory entries.. The list is endless, that person you lived as cannot just disappear and it's almost impossible to change every record that happened before you got your grc.. For instance, when I got married for the first time in 1991, same sex marriage was illegal, yet if that marriage certificate was to be changed retrospectively, that's exactly how it would seem...
So I had to just accept that that guy born in the 70s,did marry in the 90's and father a child in the 00s..that's in the public record.. But also, a girl was born then... And she did nothing much until 2020,when she got her first passport, driving licence and married a yank!
Isn't beurocracy wonderful?
As for my actual grc, I don't think I've ever used it for anything? My new birth certificate has been very useful.. And you can't get the one in the uk without the other.