This image shows the difference between 2mm and 8mm pitch rods. These are from banggood so I'm not 100% sure they're the same type that E3D are shipping:
Hmm, I'm not so sure about using the coarser pitch lead screws as this means that the bed level will become much more sensitive to minor rotational tranisitions of the lead screw, so more likely to give banding errors. These lead screws are better for faster linear transitions, which are not needed for the Z-axis.
It would be interesting to know why the change was made, hopefully there was design logic behind it not merely that they were easier to source...
Mine was shipped on June 8 with the older style 2mm leadscrews, but with Z steps set to 400/mm. Took about half an hour of dial twisting to get it up to 1600.
I share your pain! Mine was shipped may 17th (hybrid dual titan). The brass nuts have 4 screws which in the build documentation would imply the 8mm pitch and thus the 400 steps/mm, but this results in the bed not going down all the way. The firmware (hybrid dual) had 400 steps/mm2 set as the default. It took me far too long to realise they had changed things up again (back to 2mm pitch?), changing the steps/mm to 1600 solves the problem. Prepare your fingers, it takes many turns. Protip: don't get distracted while turning as the screen times out and you will have to start over. As far as I can tell they are now shipping brass nuts with 4 screws but they went back to the 2mm pitch and, as of yet, this is not documented anywhere.
I'm not sure this is a case of going back to 2mm, given your ship date it is more likely that you were at the end of the 2mm period as the 8mm rods seem to have appeared by early June.
I think the important thing, which I tried to point out earlier, is to look at the rods and not the holes in the nuts, as my May delivery had one nut with two holes and one with four, both 2mm pitch. Just going by the nuts is going to cause confusion.
Agreed, and the difference between 2mm and 8mm pitch should be very easy to see (or measure). If by accident they shipped the wrong nuts you wouldn't be able to fit them anyway so the visual inspection of the rods is clearly the most certain way to proceed.