I think a lot of people need to learn the art of patience - trust me, it’s a key skill for a future career with any part of LU.
I get it’s frustrating not knowing but these things move as fast as they move. Every time you chase up you’re only taking someone away from their job of actually onboarding things. It isn’t unknown to wait a year to start railway jobs, although I would suggest that the person who is speaking of a two year wait is at the abnormal end due to waiting specifically for CSA1 Night Tube and/or part time roles - these will only get filled as and when those vacancies become available, and there are usually significant internal waiting lists for any PT role that isn’t Night Tube. Other internal changes and happenings won’t have helped any of the recruitment processes.
Sit tight, get your documents filled in as promptly as possible and TfL will get back to you.
FWIW I had to wait 6 months from getting offered a job to starting, and the referencing and medical aspects took the longest. Once they were done things started to move more quickly, although I also acknowledge I was in a position of not needing to give a notice period.
It is worth also noting that should you ever apply for any internal promotional opportunities such as Supervisor or Train Operator it isn’t unknown to wait in excess of a year…