As I talked about in DevOps Book Club, reducing work in progress (WIP) is generally a good thing. It lets you focus, makes things more predictable, reduces time lost to context switches, decreases time to value, and in my case, makes my boss happy. The place where I have some disagreement with the idea of minimizing WIP is around bigger things and things that mostly come under the category of Internal Projects. Particularly in a larger organization. Things that require organization of lots of teams across an org or inherently have large blocks of "waiting for things to settle". If that's all you're doing you've squandering your time.
Yes, you could break things down into tiny little pieces like "Send an email to team A", "Respond to email from Team A", and "Share results with Team B", but really, the task is "Coordinate with Teams A & B". And that task inherently has a bunch of built in delays and down-time. So you can have a single piece of WIP, or you can have a couple of those coordination tasks, which become basically interrupts to the main task you're working on.
You do need to be careful to not have too many of those interrupt tasks. The whole point of minimizing WIP is to focus and keep things from becoming interrupt driven, with nothing getting done. If you're not careful that's what happens.
Back when I was doing near-real-time game coding on Windows we used to use the Windows Multimedia Timer to get things to happen at something approaching a steady rate and QueryPerformanceCounter to figure out how much time had actually elapsed between calls so we'd know how much time to simulate. And it worked really well for a while. Then we started to work on some networking and remote coordination. We'd send a message to a remote node, but we couldn't wait for the response because it was longer than our frame time. And we couldn't schedule lots of little tasks because they weren't periodic or something we could plan for. Our solution was to create a comms state machine that generally did nothing, but when there were messages to handle it handled them. In between those times it existed, but didn't take up usable time and cycles. By scheduling event handlers we were able to get lots of useful work done, stay within our time budget, and minimize overhead.
At the more macro level of project tasks and work items the same thing can be done. Most things are individually scheduled, but you carve out some time for things with lots of wall-clock time, but only a little processing time, and let it coordinate itself. And that's why I have more WIP than my boss likes. Because I'm coordinating a lot of "remote" work that needs to get done, and the coordination takes some time, but the time isn't regular or predictable on a short scale. The total work is, but not the work in the next few hours.
Net-Net, minimize your WIP. Let it increase only as much as it takes to keep making forward progress on something, but only as much as it takes to do that without negatively impacting the high priority items, thereby reducing "Time to Value".