I have a lot of faith in the data from the Energy Information Administration. It is part of the Department of Energy. It's data come from very reliable sources at it is used for taxes and import levies. The EIA is widely referenced by many reporting agencies and publications.
My guess, and only a guess, is that this report published May 4th was written in April. When it states last month, the author was probably talking about March, not April. In April there was ~1,000,000 gallons deliveried. I suspect somewhere the data was converted from barrels into gallons twice. The article states "South Korean gasoline exports to the U.S. west coast soared last month", this was not a normal import level. The the average over a year or two does not come close to this level.
But I would like to see any other data you come across.