According to the First Fifty Years Project Cornelis van Quaelbergen and Cornelis Claasz were two different people, despite having similar estimated birth and death dates.
Commandeur Cornelis van Quaelbergen
M, #7626, b. circa 1630, d. 3 February 1687
http://www.e-family.co.za/ffy/g7/p7626.htm
Cornelis Claasz
M, #6906, b. circa 1630, d. circa 1688
http://www.e-family.co.za/ffy/g6/p6906.htm
and also https://www.geni.com/discussions/143055
It's probably high time to sort this out once and for all, as you say, Private User.
Uprooted Lives (the Genealogical impact of the 'Angola' & 'Guinea' slaves at the Cape of Good Hope in the 17th century by Mansell G Upham writes on pg. 39:
Andre M. van Rensburg ['The Jigsaw Puzzle: Isabella van Angola, Cornells Claasen & Armosyn , Capensis, no. 2 [2000), pp. 9-20; Capensis, no. 3 (2000), 'The Amersfoort', pp. 5-25] incorrectly assumes Isabella van Angola and Maaij Isabella van Angola to be one and the same person and that she is the likely mother to the Company heelslag Armozijn Claesz; van de Caep. There are clearly 2 contemporary slave women from 'Angola' both named Isabella. The illegitimate halfslag
daughter Catharina appears to be the child whose biological father is originally alleged to be Kees de Boer [Cornells Claesz: (from Utrecht)
I can't remember where I downloaded the book from, but I can forward it if anyone wants it.