What appears to have happened (putting a few bits and pieces together here) is that the previous SSSS system has been widened and changed, to include swabs at the departure gate, as a result of the agreement between the USA and EU that (in the end) didn't lead to laptops being banned from trans Atlantic services. SSSS only affected a handful of people a day, and didn't involve swabs of hands and feet/socks. There presumably was a bit of a delay between agreement and implementation so that equipment and staff could be put in place. From what I can make out, this means that boarding passes don't come out on the Apps (as with SSSS) but may come out of BA.com, or may not. Either way, boarding passes are issued at the airport. I think at least for a while, we can assume this will affect a lot more people than SSSS.