Good News Everyone

No, that's what I'm saying. Black beans 'lack' methionine in that they have less milligram methionine per gram protein than other protein sources, but they don't have none.

This table in the source that I linked is to be read as "you should eat 4.59 cups of black beans per day to cover the methionine RDA (if you weigh 70kg and all you eat is black beans)":

Here's another diagram showing that black beans do contain methionine, which got published in a scientific paper:

https://www.researchgate.net/figure/Amino-acid-composition-of-quinoa-black-bean-and-lentil-proteins-g-100-g-of-protein_fig1_351804462