The location of IV systems is based on the map you are playing, not so much the difficulty. If you play the new map on a difficulty 7, you'd still have the IV system where it was, most likely. The "non technologist" random simply excludes certain AI types which use higher-tier waves and reinforcements on ALL of their planets.
Having high-level planets scattered throughout the galaxy map is something that is just native to the game in general; if a really tough one starts out next to you early on in, you may want to simply avoid it. Or, if it has stuff you want, it's harder to take as you saw -- it really depends on how you treat it, but most of the time I tend to leave those for later myself.
Hope that helps!