*It's an external database. Updates released to production last march. I can't see anyone working on local copies this day and age. It's not a software update either but a table update. I believe this is biggest global medical coding system. I know it's used across USA, Ireland and UK. And serves way more countries.
And if UK wanted to get codes for 'cake' added for covid. They would need to put request in, with rationale, have it agreed, tables updated, testing, and release to production anyway.*
Codes for Covid-19 i.e. the actual illness were released in March 2020. But the codes for the vaccines were released much later (once the vaccine was invented). Codes for administrative tasks around the vaccine may have been released even later once it was identified they were needed.
In the meantime practices may pick a random unused SNOMED code to add to records to mean the thing they want to add but currently have no code for. For counting and audit purposes. I definitely know this happens. Last month there was a panic because practices had no way of recording anything around covid booster vaccines because the codes hadn't been released yet (they probably have now).
The receptionist who posted above confirmed the cake code has been used as a substitute code for covid vaccine authorisation, so this is the most likely explanation.
Parent child relationship codes
This describes the structure of clinical coding. There is a parent code "cake" and child codes underneath "fancy iced cake" being one.