Sometimes, I share this suspicion. Other times, I realize they're going to have to fill all orders eventually and don't believe Tesla will delay a lower-margin order on purpose - they can have that tooth pulled now or later, but it must be pulled at some point.
I believe that most penny-pinching buyers like me who are holding out for $52,990-$7,500 will continue to do so, won't "give in" to the possibility that Tesla is prioritizing vehicles by margin, and will eventually get their vehicles in a reasonable about of time. If the full credit is no longer available on delivery day, then, well, there will be a lot of extra Model Ys sitting in inventory and they're going to be harder to sell without the full tax credit.
That's just my theory, but what do I know?