The apparent discrepency is caused by the conversion of SBD through the convert steem$ option in the system, which i think was james's point.
This conversion actually destroys steem$. So a net gain of 75K when we expect the system to be producing 300K simply means that 225K were redeemed.
I think the point james was trying to make is that its not necessarily accurate to say "75K were created" when thats a net gain. In the same sense as it would be inaccurate to take a situation where 10 babies were born, 5 old people died and say "5 people were created today"