I have plenty of ornamental grasses that stay put in a clump, including some which are bamboos (Fargesia, Thamnocalamus spp.)

Otherwise, I agree with your sentiment that bamboo sellers ought to be candid about the spreading prospects of what they are selling. But I don't believe there is any reality of it happening, and I probably don't want to live in the type of country which would legislate for it. The reality is that sellers can sell (most) things even in complete ignorance of what they are selling, and even if they do are under no obligation to make disclosure. Even some of the most respected bamboo sellers describe Phyllostachys as "clumping" unless it is a totally rampant one. As in everything else, it is caveat emptor.