linguistiliniw
They're fun to work with; some versions have FRAM instead of Flash memory.
IIRC it was in a trial period pre-pandemic. The impression I got was that they wanted to test a 4-day week, but worried it would be disruptive if only one or two team members were out on Fridays. Hence, 4-day teams.
Amazon gets a bad rap, but it can be a nice place to work as a developer. The overtime and pressure varies wildly from team to team, and you'd have to figure that people who choose to join a 4/3 team aren't the sort to press deadlines.
This listing looks like it is for a position which supports their internal developers and/or retail site. Those systems are probably fairly mature, so maybe it's a good business move to hire people to keep them running on a slow burn with better work/life balance.