Continuing to research to make sure I haven't missed anything I found a 1921 source about what may be similar pyramids.
"In the neighbourhood of Ngwo, Nsude and Agbaja Owa in the Udi Division, at intervals, the people construct quaint circular pyramids. Clay is used for the purpose. The bases are about sixty feet in circumference and two to three feet in height. Then another section is laid about forty-five feet in circumference and so on until the pinnacle is reached. They are erected to the honour of “ Ala ” and to indicate ownership of land.
Two rows of five are built parallel to one another which means that “ Ala ” gives children with the right hand and the left. The god (or goddess) dwells in the pinnacle and, thus, is in a position to detect any person committing evil. Such a person will be caught by the god and secured with shackles ; these are represented by small sticks inserted in the clay near the tops of the pyramids."[https://www.google.co.uk/books/edition/Among_the_Ibos_of_Nigeria/hKssBgAAQBAJ?hl=en&gbpv=1] P.109 This is the book ''Among the Ibos of Nigeria An Account of the Curious & Interesting Habits, customs, & Beliefs of a Little Known African People by One who Has for Many Years Lived Amongst Them on Close & Intimate Terms''. 1921

This doesn't of course contradict my source above, just shows that these are earlier. We can't know how often these eroded and were replaced.