While checking on the appearance of a plant listed as Neomarica longifolia in a published article in July 2013, I got into this mystery on the true identity of the yellow flower plant in this page. This plant seems to be Neomarica longifolia but also appears to go by another botanical name, Trimezia martinicensis. Both are accepted botanical names. Eventually, I reached the Pacific Bulb Society page, which I believe correctly demystified this confusion.
After further search on the appearances of Neomarica longifolia and Trimezia martinicensis. I realized that I had actually come across Trimezia martinicensis back in 2011 but thought that it was Trimezia steyermarkii then. As for the authentic Neomarica longifolia, a picture is available at the Brazil Plants website.