The miner used to have JUST enough slots to hold everything. With the advent of multiple stone types (Diorite, Granite, Andesite), 3 additional slots are taken and it is likely a miner will run out of space.
Why this is significant: Where before a miner might have taken up 2 slots with 64 cobble and 26 cobble, now it might take up 4 slots with 51 cobble, 1 Diorite, 20 Andesite, and 18 Granite. In a recent real-world test on level 49, 15 slots were filled with cobble x5, Diorite (1 block), Andesite (20 Blocks), Granite (18 blocks), dirt, tin, lead, copper, iron, uranium, redstone and coal. There is still the possibility of diamond and gold, and we are already at 16 blocks. I removed 3 cobble to make room for testing to bedrock, or else the redstone would have been on the ground.
I know a chest and an ejector would also work, but if that was the point, why not have no space at all? I feel the space is there to allow a miner to hold all items at a significant level above bedrock.