I know you weren’t asking for my opinion, but since I find it difficult to pass up an opportunity to talk about Say’s Law, here are my two cents:
“Production must precede exchange” can be restated as “supply is a necessary condition for (effective) demand”. But it’s pretty clear that “supply creates its own demand” makes a stronger claim – namely, that supply is a sufficient condition for demand. So the short answer is: no, those two phrases are not the same at all.
