Interesting question, I can't wait to see others opinions on this.
IMC knowledge local is most definatly tied to a local, otherwise it is knowledge world. I work it like the 2e NWP used to work. The 2e NWP works like this, you take Knowledge local and then you add locals to it. You come into an area and spend some time studying the local history, geography, etc. and you gain that area to your skill. I rule that you are allowed one local for each rank in the skill.
Basically I view knowledge local as knowledge geography, nobility, history, etc. It is basically what someone who lives in the area for a long period of time would know but this profession allows the people to get that with only spending a week or so of study. So overtime and with travel a character can expand their knowledge local into a skill to know the entire world, but that takes a long time and a lot of travel.
Hope this helps.