Regarding question 1, as Frimmel said, it’s important to not bring any baggage from other A&A games into the “battle” games, as their mechanics are very different. It would be inadvisable to point out those differences in the Rulebook, though, as that would simply confuse readers who have never played a strategic-level A&A game. It’s best for experienced A&A players to simply look at these games with a fresh eye, and it probably would have been good for the Rulebook’s author to note this in the introduction.
Regarding question 2, the reason why there is only one box on the Supplies combat strip is that, unlike with the combat units, there is no fixed stacking limit for Supplies. The combat units’ combat strips can have a fixed number of boxes due to their stacking limits, but the number of Supply tokens that can be in a hex is theoretically unlimited. Perhaps having an image of multiple tokens on the strip would reinforce the idea that multiple tokens may be hit, but the rules do clearly state so.