So, when "Bloodline" talks about the New Republic encompassing almost every system in the galaxy, I guess I'm just supposed to assume they're not referring to the Uncharted Regions? Makes sense but it still needed to be said in the book.
Well it's like saying something like "the whole world saw such-and-such an event", which is on the face of it damn near impossible, but it's a given that it's not meant to be taken literally, down to the last person. Or just the phase "every country in the world" in reference to *anything* is inherently troublesome since there's always a certain percentage of countries who's status or very existence is in flux. And yet it's a common enough phrase since the alternative would be pedantic.
So yeah, in Star Wars when they say "nearly every system in the galaxy", it's best to take the word "galaxy" not as a geographic (astrographic?) label, but more of an abstract idea the same way we might say "the world". It's all encompassing, but not really when you get into the shockingly numerable caveats and exceptions.
In regards to the Star Wars galaxy, there are plenty of fringe regions, isolated pockets and long forgotten planets that the idea that "every planet" can even be accounted for is dubious at best. Yet, the phase would logically be in common use since everyone knows what it really means. What goes unsaid is every planet *that matters*.
All of that is not even counting the massive swath of the western end of the galactic disc referred to as the Unknown Regions, every last little backwater in the Outer Rim, the lost colonies, primitive worlds, uncharted systems too far off the hyperlanes to be worth bothering with, the isolated regions of Wild Space or anything in-between.
