I just installed exactly the same pedal on my bike and plan to ride it for the very first time tomorrow. I have exactly the same issue/problem with my right pedal. The left pedal spins smoothly by hand, while the right pedal does not spin as smoothly as the left. I think it's the way the pedals are, and I am thinking the right pedal is gonna free-up with use.
I also just took delivery of mine from Probikekit.
From my experience, Shimano does tend to pack too much grease in the bearings of their new pedals and hubs. In the last year or so, I have had the same kind of experience with two sets of Shimano SPD M-520 pedals, a rear Shimano XT hub and a rear Shimano Dura Ace 10-Speed hub. They all got too much grease packing from the factory, to the extent that some grease oozed out on the first week of use, but since then, no issues at all.
So, think too much grease packing in the pedals.
It should spin and get better with use.