Okay, let me clarify. The advance scouts tech makes all your unscouted provinces easier, both to fight or to cater, but not the ones you've already scouted. The Squad Size upgrades give you more troops. So even though the provinces that you have already scouted stay the same level of toughness, fighting will be slightly easier because of your squad size upgrades. Catering those scouted provinces, however, will be the same as they were before you got the tech ... no help at all. In other words, over scouting causes those provinces to be harder than they would have been if you had waited.
Now, one thing you have to balance, though. I don't research any of the squad size upgrades that are optional. I skip those on purpose, because even though they would make province fights easier (if I fought instead of catered), squad size upgrades can hurt you if you do tournaments. So if you're a heavy tournament player, you may wish to avoid squad upgrades whenever possible. Just a thought.