It can be a gimmick, but it does not have to be.
The important question is whether bamboo fiber is actually part of the commercial formulation or simply part of the packaging design. A credible supplier should be able to document the bamboo fiber percentage, explain its function in the material, and provide finished-product testing.
Adding bamboo fiber also creates engineering challenges. Fiber dispersion, moisture control, film consistency, heat sealing, and puncture resistance all have to be managed.
I would not judge the product by the word "bamboo." I would ask for composition data, test methods, finished-product performance, and clear disposal instructions.