Some agencies call the day off a RDO "regular day off". Some call it "AWS Day" reflecting that its the day off that comes from working an alternate work schedule. My first job called it AWS, so I still call it that. My current job usually calls it RDO, but idc and still call it AWS day.
In general AWS are popular in my agency. Those that "grew up" here stick with a normal 8hr 5 d/wk schedule. It's only the few of us that came from elsewhere that use a AWS.
Yes I work a 5-4-9 AWS schedule. I was clear up front during the hiring process that I wanted it as a condition for accepting the job. I was allowed to do it after the 90-day probation period. Having to work all those 5 day weeks really messed with my internal calendar, and I was really happy to get my alternating three day weekends back.
There are also a 4x10 AWS, four ten hour days/week. There's CWS and maxiflex schedule which is basically just working 80 hr/pay period with varying limitations. No one at my current job does the 4tens. But I might switch to that after we're done with this mess. No one does CWS or maxiflex either, or at least not regularly. Technically I do maxiflex twice a year, but that's just an administrative artifact due to the holiday calendar - and for all intents and purposes I maintain a 5-4-9.