LC, there is a legitimate shailah about the definition of kitniyos and what falls under that category. Those who hold that the minhag wasn’t limited to specific species hold that if something has the characteristics of kitniyos, it falls under the issur. The “ever expanding list” is simply a matter of some species which weren’t eaten until recently, and are subject to analysis of whether or not they fit the characteristics of kitniyos and are therefore assur. It is a legitimate halachah shailah, nothing more or less, certainly nothing sinister.
The OP, as I understand her, was simply asking why, as the powdered form resembles flour, (perhaps she also meant since they are called beans) they don’t fit that category. She wasn’t trying to asser anything, just asking a question.
Of course, despite their name, they’re botanically not beans, but as I linked, the Shaarei Teshuvah brings one opinion (which we don’t pasken like) which actually assers coffee because of its resemblance to a bean.