Anyone have a link, or otherwise have evidence for this idea?
It seems to be true for most (but not all) African games in general. There are reports on Omweso saying that the opponent may turn over a board after counting to three. In Shax, a professional is supposed to play at blitz speed, including when playing another professional. A document on Ghanaian Checkers on Scribd states that thinking long is not an expected behavior. It is not exctly Africa, but youtube videos show Hawalis players in Oman at blitz speed as well. They often start their counter move while the other player is still moving. Going back to Omweso, the article in Abstract Games Magazine gave the score of a game between professionals in which one player moved twice in a a row for that reason. It confused himself more than the opponent and he lost.
There are exceptions, however. Bao profesionals handle the opening at blitz speed. But on some occasions, players can and will take time for thinking.