Because the globe model is not accurate at all, south of the equator.
To illustrate this easiest, there was a group that was going to sail around Antarctica.
So, on a globe, you should easily make that journey in a month.
After a year, they gave up and turned north.
Every time they took a reading, they found that they weren't as far along as they thought.
So, if you try to sail around South Africa by going so many nautical miles, and then turning north you find that you haven't actually gone far enough, and you turn north and smack into land.
(it is not a "little" pear shaped.)
I have never been south of the equator. I can neither confirm nor disprove your claims from personal observation and experience.
Who was this group of antarctic circumnavigators? Where can their records be found?
Africa is a lot less pointy than South America on every map or globe I have seen. Are you sure the flaw is not in your conceptual model?
And this is where i fail bigly. I do not remember names, so i cannot provide search terms for these events.
It is that, when you take the globe model, and you are at a certain latitude, then the distance between longitudes should be X, but, south of the equator this doesn't hold true.
When you measure distance across land from one degree of longitude to another
When you try to sail around Antarcitica
When you try to sail around a known land mass (the bottom of Africa)
You find that it is not X distance, it is 2X or as you go further south it is 12X
How do you know this, though? I do sympathize with not having sources at your fingertips. I read a lot, online and off, so having info rattling around between my ears with no easy hyperlink for a source does happen. But extraordinary claims require extraordinary evidence. Sure, in the end, we're both working from hearsay when it comes to distances and travel, but the preponderance of evidence I have seen which people support with data (whether dubious or not) does not match your unsubstantiated claims.