You've come upon one of the "gray" areas within the classic commemorative series. This particular one is the result of the large number of BTW half-dollars that were returned to the US Mint by the Booker T. Washington Birthplace Memorial Commission for melting. Accurate date and mintmark records were not kept for the coins that were returned/melted. This has led to various researchers and authors estimating the numbers and causing differing net mintage statistics to be published.
Let's take the 1946 (P) coins as an example. It is known that 1,000,546 business strike coins were struck, with 546 reserved for assay purposes and not distributed. Q. David Bowers, in his well-researched
Encyclopedia of United States Commemoratives: A Complete Encyclopedia, estimated that 300,000 1946 coins minted in Philadelphia were melted - this would leave a net mintage of 700,546. As Bowers is now directly involved with the publishers of the "Red Book," it makes sense that they would use his estimates to update their listed statistics. In earlier editions of the "Red Book," the 1946-(P) mintage was listed as 1,000,546 with a note about an unknown number being melted. The story is the same for the 1947 issues.
The Krause
Standard Catalog you referenced shows the original production figure for the 1946-(P) (and 1947 issues) without including estimated melt figures (they cover themselves with the note they included at the top of the mintage/value table).
There are other US commemorative references that present mintage statistics that differ from both of the references you listed. For example, Anthony Swiatek recently authored an update to his previous books on US commemoratives and included an estimate of 500,000 as the number of 1946-(P) coins that were melted; he lists the net mintage for the coin as 500,000.
I would recommend you consider the net mintage figures presented in the "
Red Book" as the more reliable. They may not be 100% accurate (due to the melted inventory issues described above) but they are a closer approximation of the final numbers.