untopped hollow core plank diaphragm

[structSU10]

I have been searching for a while and cannot get to a definitive answer - For a building that is seismic design category C or lower in NY, is a topping slab required for the diaphragm? I haven't found anything that explicitly state untopped is not permitted, but don't know if I am missing anything.

 

[Sawbux]

I believe they can be used as diaphragms, but would be hesitant to rely on the grout keys to transfer any of the shear load. I would calculate the shear requirements and then design keys to tie the planks together with rebar dowels. The capacity can be calced using shear friction methods by ACI.
Notching out edge voids in adjacent panels and grout in bent rebars to create a key is commonly done.
Also the supplier can cast in weld plates - this is done with double tees, but not common with plank.