Originally, Kylong Plains was going to be a slightly lower level region and was therefore at T7 harvesting area with the same nodes as KoS. However, during early beta the level ranges were raised and when the adventure content went up, it made sense to shift the nodes to T8 also.
It's possible that the required skill levels on the nodes weren't changed at the same time. OR, it might be (as speculated above) that this was intentional. I'll ask around. However, the dev who placed the nodes is out this week and the other person who might know is off sick, so may not be an immediate answer.
LINK
(DominoDev) Re:harvesting level for Kylong Plains
