Nothing has changed since the entry was made. It was proposed in error and approved in error. It never belonged in the database as K. x houghtonii. There have been times when we've approved new plant proposals only on the strength of the plant's inclusion in The Plant List, even if only with "unresolved" status, as in the case of this plant, but a plant can't remain unresolved forever. If no other taxonomic database includes it after a few years, it's not a valid name.
Your first link didn't work for me. The second one did, but it's dated 2008 and lists the plant as a "self-sustaining hybrid." The fact that it still hasn't been added to the taxonomic databases as an accepted hybrid taxon in the past 8 years is an indication that it failed to meet the criteria of a hybrid occurring spontaneously in the wild. I didn't look at the rest of the links, but it's enough for me that the plant is not listed as an accepted name in the Catalogue of Life, The Plant List, ITIS, or GRIN.
