I don't know all of the calculations Apple used to determine the right mix of capacities to make, but I'm pretty confident it wasn't about tricking people into upsells.
The same assembly line or lines makes every iPad model. Making more of one means you're making less of the others. My guess (could be wrong) is that higher capacity models have higher profit margins per unit. If that's correct, it would be painful for Apple to have early adopters get downsold because the 64gb or 32gb unit they wanted wasn't available, so they get the next mode down. They are probably more worried about that than they are about the opposite situation, but that isn't the same as plotting to make it happen.
Also, when I was in line, Apple Store employees kept walking around asking everyone what capacities they wanted. The reason was so they could start warning people who joined the line later that their preferred model might be sold out. Very nice of them. But the reason I bring it up is that the people I could hear answer seemed to mention all three sizes about equally, with 32gb probably the least common answer by a small margin. Obviously this is not scientific, but I think there was also high demand for the 64gb version by people who either just don't want to worry about it, or who want to load a lot of media. If I'd done less research, I'd have gotten a 64gb "just to be safe".