Should you not also include Spain (Ceuta, Melilla, Canaries), Italy (Lampedusa, Linosa, Pantellaria), Portugal (Madeira), UK, (St Helena, BIOT) and France (Mayotte, Reunion)?
For the same reason you wouldn't include the U.S. in Oceania, or Russia in Asia, or because f*cking common sense? they all have European capitals, cultures, populations, and mainlands. Those are just territorial ownerships, even with cases the French Guyana, you wouldn't call France a South American country.
I mean to some extent French Guiana is a part of mainland France. If someone were to start an argument over if France should be classified as South American this would be a strong point for their case, but I see both points. Not protecting or going at someone just pointing something out.
Um...I found something. When you type"Bissau" and then type"Guinea" it gives you both Guinea and Guinea-Bissau for every quiz that includes both countries.