In answer to my question,
http://ozreport.com/17.235#1, about why a World Record isn't also a
Continental Record, Octavio Fiães <<ofiaes>>
from Brazil writes:

The reason why a world record set in South America not be also a
South American record is because the rules of FAI only consider continental
record when they are set by pilots with FAI license from countries that are part
of the continent in question.

In Section 7-D of the sporting code:

3.5) Continental Records

 3.5.3) Eligibility

  Only pilots who have a FAI Sporting Licence issued by a nation which is a part of a particular continental region may set a Continental Record for that continental region.

 3.5.4) Qualifying Flights

  3.5.4.1) Where Flown

   Continental Records may only be claimed for flights which start within the continental region for which the record is claimed and the majority of the flight is made within that continental region.

http://www.fai.org/component/phocadownload/category/?download=2826:s7d-rb2011v3