I don’t think you need to worried about voicing such a generalisation. It only matters if you use it in order to prejudge or discriminate.
Certain physical characteristics are prevalent in certain groups. In African it is likely that we have much more genetic variation between tribes and areas than we do in all of the “out of Africa” populations as a whole.
That’s simply because Africa came first and the diversification of the population has been going for so much longer. It is pretty much what you would expect. So not surprising that we can express what we mean by a “typical” Somalian. Equally not surprising that such characteristics are an imperfect definition. They can be shared by others outside of Somalia and not shared by some within Somalia.
So if you use that physical checklist as a means of amusing yourself and seeing if your guess was correct, fine. If you decided to discriminate on the basis of the guess…not fine.