Nope, it doesn't. The friend just needs to either pay in or transfer in a minimum of £500 in total within 120 days of opening their new Dodl account. Remember though, the first one-off payment to a Dodl account needs to be a minimum of £100.
Before the voucher codes are sent out, Team Dodl will do one final check to make sure the new account balance is at least £500, otherwise the codes won't be sent (sorry!). Check the T&Cs for more details.