They don't need to say it, but because they said the 'minimum' is a 2:1 / 3 GPA it doesn't mean that you will be considered for an interview. If too many people basically applied with the minimum at Imperial, they will just select those with the higher results.
On the safe side, I intentionally said '3.9' GPA / high 1st because it totally beats their requirement of a 2:1 which the competition will try to match. If anyone is seriously considering this university, they should instead get a 3.9 GPA, not a 3 or 2:1.