They're testing against a hypothetical user on a 2G cellular connection. I can't see many situations where that would happen. Being poor doesn't mean you can't afford 3G because every data plan in the UK includes 4G as a mimimum. Often 5G is included too. You have to be extremely rural to drop down to 2G and rural people are often better off. Poorer people tend to be in urban areas that have better digital infrastructure.