DDR4 ECC ram?

I never noticed this before....but apparently all DDR4 ECC memory like this. Notice the curves on the pin side. These 8gb modules were pulled out of a brand new HP G9 server. The 32gb modules I put in have the same curves. I assume memory slots have the same curves preventing adding incompatible ram?

EDIT:  Turns out this is indeed by design!  I am told it is to limit the amount of force being applied to the system board during insertion.