The science on plain wood being safe has been around for quite a while. I remember reading a study many years ago where some scientists mashed bacteria all over the surface of a wood cutting board, rinsed it, dried it, and then tried everything they could to get the bacteria to transfer to fresh meat (including trying to pound the meat into the board with a mallet) and the meat remained uncontaminated. So, it seems like the safest option is a single unglued plank of wood.

Glue joints don’t act like wood, so presumably that makes bamboo act less like plain wood safety-wise.

The problem with plastic is that the knife marks can retain bacteria (which, unlike wood, the plastic doesn’t kill).

I'm going to hypothesize here that bamboo works similarly to wood in the "wicks water and bacteria in, bacteria get stuck, water evaporates out desiccating bacteria to death" mechanism. The issue I see is the whole "glue joints are bad" thing from the article. Because bamboo grows in hollow tubes, there's no such thing as 12/4 bamboo, you have to glue up a bunch of tiny pieces, so there are lots of glue joints.