Having logged finds in South Africa in the meantime I have to correct myself in as far as the Africa map seems to behave slightly odd, indeed:
Before my recent finds the map showed correctly 1/53 countries found.
Now, having added South Africa it still says "1/53 country found in Africa" in the line above the map, but underneath the map it correctly lists both countries, however not in the standard order (according to number of finds): South Africa comes first with (currently) 22 logged finds, Spain/Islas Canarias second with 168 finds. The latter ones are also not plotted green on the map.
I assume the problem lies with the special circumstances regarding the islands. Contrary to other colonial / oversees territories they don‘t have top level ("country") status on geocaching.com and hence PGC, therefore I am very impressed that PGC correctly identifies them (and just them, not the rest of Spain) as being geographically part of Africa. Thanks a lot for this! Having this in mind I don’t know whether the tiny issues with the Africa map described above could be solved?