Yup, if your hubs were unlocked in the video, that is exactly why they were able to rotate a small bit, due to the backlash of the gears in the diff. I see no issues.
If the hubs are unlocked, then that means the axle shafts can move freely, but they are still limited by the gears meshing in the diff, and the gears are meant to have a bit of play between the teeth (called backlash). The backlash is what is allowing the axle shafts to rotate back and forth a bit.
The axle shafts will actually sit there and not rotate at all when you drive because the hubs being unlocked means the wheels can't rotate the axle shafts. Which is also why when you put it in 4WD, you have to get out and lock the hubs, to engage power to the wheels.