It is extremely doubtful that the script couldn't keep up with such a small amount of transactions.  Probably what happens is the IPN is looking at the transactions in order it sees, but it is a massive race state around the globe until the transactions are planted into the blockchain.  There are probably multiple versions of lists until a version is accepted by the node that blockchain uses.   Maybe they exist differently for a very long time.  

Additionally around GMT 00:00:00 I did a series of transactions.   There is a wide variation of when they are listed in the blockchain.   The lowest times I saw was 2 seconds, the longest was 6 seconds with most times either 3 to 4 seconds.  

Today the play out time period was less than 3 seconds, which is less than the variation seen in just sending transactions and when they end up on the blockchain.   At this point one would be better to just play a dice game since the overhead is lower and the results are mostly random.   ~1% for a dice game vs 6.5% for the Ponzi, based on the deposits.