A great piece of organizing circumstantial evidence, @harpooninvestor, and I buy your conclusion, for a reason (adding to all of yours). From Day One the code code could not be so buggy that everybody would laugh at the loopholes. It was not, and that was probably because a bunch of guys were checking it out carefully before allowing it to go public.
Very nice, and cheers!
P.S. I am an experienced programmer, and know from long experience that once you let your program to go "work in the wild" it is likely to encounter combinations of data structures (or data volume) and logic quirks in your code that will give you heartache. So when they first went public a lot of testing was probably already done.
RE: Did Nick Szabo solve Nick Szabo's biggest bit gold problem?