Seems a clever marketing tactic to rope in more people.

How do you confirm address? ‘I moved home to my parents last week’ etc.

You have to buy a ticket - presumably you have to commit to an address somehow at that point, so people can only buy for one postcode even if they're lying. Unless there's a skewed outcome that shouldn't really matter. (And if there is a skewed outcome...the people who'd bought the winning postcode and didn't have a house on that street would be under heavy scrutiny!)

Apparently, at least in NL, you can buy for different postcodes even though most do not.