[brudgers]

In the abstract, I don't see an obvious practical advantage of 3d steganography over 2d because the tools for 2d (printers and cameras) are more readily accessible and the processes of creation and reading are faster...particularly reading.

There might be corner cases where 3d makes sense...but it is hard to compete with decals/stickers, and 2d steganography can also use color and saturation as additional data dimensions.

But I could be wrong.

[Intralexical]

The advantage is much more durability. Hardier materials, and the print can lose an entire paper sheet's worth of mass/thickness, and still be readable.

[brudgers]

Those properties sound beneficial in non-obvious corner cases.

In particular those when a sheet of paper’s thickness does not impact the required data density. While storing data on a wear surface is desirable and necessary to system design. And when conventional use of a engraved number as index to extended data is insufficient.