I think you misunderstand their point. PostIdent would only be useful AFTER someone took the time to rate the game. Steam does not require any official content/maturity rating in their store, just some subjective content descriptors. To do so would pass an additional cost onto developers. The US-based ESRB process, for example, can cost hundreds or thousands of dollars to rate a title.
Further to your point, I try to limit the number of times I provide my personal ID online. It’s one thing when you show your ID at a bar and the bartender gives it back to you after a glance. It’s another when I’m sending a photocopy over the internet and trusting a remote, distant party to use the data once and discard it. Even worse if they save it for future use and risk leaking it later.
I think this is a perfect idea for a Youtube channel. Maybe in Alt Shift X’s style. Just go through popular shows (ongoing or finished) and recap the big ongoing plot lines, characters, relationships, etc. One at the end of each season, maybe even one at the end of the series just for the sake of completion.
I saw a recap like this for the show Dark and, well, I was still lost through most of it, but it’s a good idea. That show’s a bad example.