I am no CBP fan either, but has anyone considered the case that these are counterfeit AirPods in counterfeit OnePlus earbud boxes? If you look at the opened box picture in the CBP memo, you will notice the earbuds do NOT match the picture on the OnePlus box and look much much more similar to actual AirPods.
The thing that caught me (and maybe you) is that the OnePlus pods have a flat part, and the CBP pictures have no flat part. But looking at the pictures from the review, the flat part is the end of the stem, and then the bulbous round part that goes in the ear is attached to the stem, with the flat part on the other side. The CBP pictures may have the flat part facing away from the camera.
I had to look at several of the pictures in the review which showed two pods next to each other to build a mental model of their shape.
[1] https://www.theverge.com/21331910/oneplus-buds-wireless-earb...