I'm sorry, but this story of the introduction of the potato in Europe seems to be off by quite a bit. Pizarro (Spain) discovered the potato in the Andes in the 1530s, where it was cultivated as a food crop by the Inca. There were no potatoes anywhere the Portuguese went in South America so Frois might not have heard about it at all in 1569, but if he heard about it it would have been as food, as the Spaniards who discovered it were well aware why the Inca were cultivating it and did so within a generation themselves. The Spanish brought the potato to the Canary Islands in the early 1560s, and the first exported barrels of harvested potatoes from there arrived in Antwerp in 1567. The English imported their first potato plants from South America a couple decades later.
Of course there might have been some royalty or other important people who were gifted potato plants that they didn't know much about. That still seems strange for something that was known as a food crop from the start, and would soon have been cleared up as the potato was introduced as food within a few years of its crossing of the Atlantic and immediate cultivation in the Canary Islands. And of course there would be some who tried to eat the wrong parts of the plants, just like in England during WWI when some tried to eat the leaves of the rhubarb plants as a replacement for salad. Don't do that, eat the stalk only.