This is because of these incidents.
1. Once on an MTR train I heard the national anthem by accident and I immediately stood up in front of ~100 people on the train, looking at one of the TV screens which played the anthem. Everyone on the train looked at me and they told me that I will absolutely have no problem with a new bill about national security!
2. In 2019, I intentionally picked the mainland CR400AF train over the HK-made CRH380A Vibrant Express when I was travelling on the High Speed Rail.
3. I always sing the national anthem with passion and I was always the only one who stood up for it in the class. I once stood up for it 7 times in one evening when different TV channels played it before their news reports (Viu 99>TVB 81>HK Open TV 77>TVB 83>CATV 9>CATV 8>RTHK 31)
Do you think this is true?