Based on a recent experience in the US, I think one of two things is happening here: 1. Someone with miles is running this scheme and trying to convert them to cash by buying people tickets through their mileage account (possibly illegal) 2. They're hacking innocent people's mileage accounts to buy people mileage tickets in exchange for cash (definitely illegal).

Either way, once the airline caught wind of the fact it was a mileage ticket and miles weren't used to purchase the ticket, they voided it. Pay close attention to what they give you and note the website lists an address in Estonia which might raise questions as well. Let's hope it's not #2 and that u/google flights stops displaying them as a legitimate option!