I coined the expression "singular focus" as a way to stop multitasking across too many projects. In times of stressful work scheduling, even the two slot model is too much for me to handle, so I drop being responsible for the second slot. Usually this is something related to a personal project or well being, so it was not a great strategy. It's more like something that must be done. In practice, other things still HAPPEN, but they aren't scheduled or tracked. In all of my personal production models, I have to allow quite a bit of random activity anyway because that's how my brain works.
Singular focus sometimes requires hermit mode.