I have a Russian recording of Symphonies 1 & 3, which must have been made prior to 1956, if the conductor's name is correct - so the complete ms should've been available for some time.
That's interesting indeed as I was almost positive they were completely unrecorded until the two recent ones. But then I thought the Naxos recording of Creston's first symphony was
its premiere too until I learned of an LP of that work from the 1950s. By now I should know better than to say "first", I even try to write "by" (by date x rather than date x, I mean) on IMSLP "first publication" and "first performance" fields unless I am pretty sure I know what i'm talking about

... but the temptation is strong...