It's just what I've noticed. They don't exactly have the best chins. I don't see any granite chins on the list put it that way
Granite maybe not but there's a wide swath of space between a true glass like Indongo and someone like Tete (at worst above-average/solid) ...plus for a long time sub-Saharan Africans had the reputation of being teak-tough journeymen (particularly Ghanaians) and of course there were durable elites such as Ike Quartey, Kassim Ouma, etc. Glass jaws, on Indongo's level, are relatively uncommon.
Isn't this the second fight involving Makabu that's fallen through? Sucks, as I love to watch Makabu fight. For what it's worth, I saw him beating Perez by decision or late KO. Perez is tough and skilled but Makabu has a habit of getting to fighters with his sharp shots at some point in the night and putting them down for the count.