Matt Hancock wants for everyone to have to use their passports in order verify their age but one big issue with this proposal is that many people don't have a passport, especially children. This would to many people no longer being able to use social media websites due to a lack of a passport.
Basically, Matt Hancock wants everybody to have to use a passport to sign into social media, for this, he is using the classic think of the children argument. If you want to know the true intentions of a law like this than just read this section of the article "under proposals being drawn up to tame the "wild west" of the internet.".
This talk of "age-appropriate material" and "time cut-offs" combined with wanting your social media account tied to official ID should have you worried as the government are very anti-free speech. This will make it easier for the government to arrest you for saying anything "offensive".