Anyone can shot this level of video, because it is not from a pro.
This video was shot with 37mm thread ND Filter
when there is a cover for it, it could be a custom lens set for specific phone model, say:
This universal 37mm thread Neutral Density Filter is universal for smart phones.
SKU LINK: DCK005547-37
Here is the video we took
A reference picture:
You can find more at www.dckina.com