It's just strange how that could happen based on how oil pumps work. If they're built crappy they might not pump as well as higher-quality ones or maybe wear out prematurely but being completely unable to pump at all doesn't really make sense. It's something that's easy to check as well, not many parts to it. I have an SA-Design book, How to Rebuild Small-Block Mopar that was published over 10 years ago and even then the author strongly recommended to always pull the cover off of a new pump to check the internals and measure clearances before bolting it onto the engine.
Maybe it was something as simple as the relief valve being stuck open from debris which you could have found and fixed by taking it apart, cleaning it and putting it back together. If it was full of metal shavings from manufacturing maybe you inadvertently pumped some of that junk into your engine while running the starter for 10 minutes.
