The African pictures also look like African people, such as the traditional dress of the Tharaka people of Kenya:

https://www.gaiafoundation.org/app/uploads/2019/05/DSC_0150....

The book is explicitly depicting people from abroad, not African-Americans. As Dr. Seuss’s surviving family has attested to his character and wordliness, and his other books like “Horton Hears a Who” promote tolerance and the acceptance of minorities, I’m inclined to go with a simpler, more innocent explanation for these images.