cell-level fusing is useful on an ebike pack because it might be involved in a crash. If one cell is dented, it might experience an internal short. Nothing will stop that one cell from going into a downward spiral, but a fuse can separate it from the rest of the paralleled string, which eliminates an overheating incident with the rest of the P-string (except maybe the risk of the actual heat from the erupting cell)
Obviously, a power wall will not have a crash, but...this is also where many builders use partially-used cells...which is actually a great use for their remaining life. Used cells will experience a wide variety of amounts of heat from the discharge peaks. If a sensitive cell gets a little too hot, it can go into a death spiral, even if the amp-draw isn't that high.
If you have an un-restricted dead-short on an entire P-string (because one cell develops an internal short, and the heat shrivels the internal separators), then...A large P-string has a huge amp difference between normal amp-draws from each cell, and the max full P-string short. If one cell has an internal short, it causes the entire P-string to react as if the bad cell is suddenly replaced with a fat copper wire.
This means that on an ebike pack (high-amp cells, maybe only 4P), the fuse selection is much more critical, but...on a large powerwall (low amp cells, 10P or more), there is a wide range of fuse materials that will work just fine.
If you are using individual cell fuses, you can put a fat copper wire between every two cells for the series connection...(of course, that would work best with an even number of cells in the P-groups)