This is not new (The product has existed for a while) but this is the first time I see it working for international routes. Only a few selected routes though.

The pricing is not bad at all IMHO. For example on the ATH-DUS route, purchasing 10 flights (5 roundtrips) allowing booking until the day of departure, is only 78 euro per flight (plus taxes). Booking further out is cheaper but has a little less value imho. The ability to book basically until the very last minute, for a set price, is very powerful - especially for summer time!

I do wonder if these flights would allow upgrading though. That'd make it a very good deal (assuming your route is on offer). The miles you'd get for these flights is already pretty good (almost 2K on the DUS route).