I am pretty sure that true SLC would be used here. When it's being used as memory and the tech itself is a ticking time bomb, picking the time bomb that ticks slowest is the best option.
It's simpler to fuse off an entire cluster. Intel has never made an E core in a cluster of 3. It's always been 4 or 2. Either the segmentation doesn't need clusters of 3 of E cores or it's impossible.