I'm flabbergasted that the Natural Semantic Metalanguage people have actually gone there, and tried to reinvent Basic English as Minimal English. I'm not surprised Cliff Goddard is behind the effort; he's always been an evangelist for NSM.
In context, the list of words that derives from is a list of candidates for inclusion in the Minimal English vocabulary, rather than the definitive list of semantic primes that precedes it; and you can tell: it clearly has not been rigorously defined or cleaned up. Goddard admits that the list is a grabbag. I think the inclusion of telephone and phone is just poor editing.
As for corn/yams, the list in context is: meat, rice, wheat, corn, (yams etc.); I surmise the actual intent is "any number of starchy staples, which could be expanded by region" (so "yams etc." are an extension of the set "rice, wheat, corn"). Again, this is a thrown-together list of candidate words, so they don't seem to have felt the need to pare it down.