Yes, you are right. I do understand the difference between the two. But the result is the same-confusion. So it doesn't really matter what the source of confusion is. If the goal of any action is to confuse, it must be stopped immediately...
To the original poster: Don't simply accept the "common knowledge" figures regarding American estimates of casualties if there was a home invasion. The vast majority of the estimates which talked about a million US casualties were brought into the political arena AFTER the bomb had already been dropped.
The Joint War Plans Committee estimates were roughly 50,000 dead and up to 175,000 injured; with the entire war over within 2 years; a high price of course.
This is a very complicated subject; be suspicious of the motivations behind figures/rationales. No political decision is ever made with only one object in mind, there are always lots of countervailing interests at hand. With respect to the USSR, remember that the US invasion plan required a secondary soviet attack into northern japan. the US did not want a rehashing of Germany, when the Soviets rushed in and refused to leave; Japan was too important to our future.
I would recommend reading "prompt and utter destruction" by samuel walker; he does a good job of detailing what was going on INSIDE the administration when the decision was being made. GOOD LUCK