I am making an educated guess, but the new TNGFA forced the Sequia into a solid rear axle, which killed the entire space. This is counter to what the Expedition and Tahoes did. By going to the rear independent, they really opened up the cargo area...trade-offs.
Now adding the new hybrid, it destroyed all remaining usable space. The battery in the tundra killed the under-seat bench storage...huge miss IMO. I can understand why they placed the battery inside the car and placed it central so as to not disturb the weight distribution too much. However, DAMN...one compromise too far IMO.