If you look at the actual data, tofu had the third lowest concentration of microplastic particles per gram (0.03, vs 0.02 for pork loin chop and 0.01 for whole chicken breast).

The press release does a disservice to the study by referring to the highly processed group as a whole and not excluding tofu. For reference, the breaded shrimp and fish sticks were measured to have 1.2 and 0.26 particles per gram.

Table 3.7 https://www.sciencedirect.com/science/article/pii/S026974912...

Regardless if a processed food like tofu has minimal plastic concentration, I would assume minimally processed whole plant food like beans and nuts would also have low microplastic exposure. The study found little total plastic from packaging, their evidence pointed towards the processing.