That requires the booster to be treated as proof of vaccinated status for 9 months, it doesn't predict that proof of additional shots will be required in the future. Which makes sense, as we don't have the information to make that determination!
There's good data about the booster being an effective booster. There's not much data about whether another one will be beneficial (neither in terms of whether it will help immunity or whether there will be a lot of virus in circulation...).
If my vaccination pass expires then I can't go eat, get on a plane, go to work. So it's a requirement to get another shot, the politicians/government just didn't say it out loud - typical.
Last time I got the vaccine for covid I was promised 5 years. It was reduced to 5 months post-facto. Do you seriously expect me to believe it will be at least the advertised 9 months this time - or that it's going to increase?