The following is a CIA report dated 1955, which describes that even as late as 1954 the Soviets were taking the most extreme measures to safeguard the secrecy of the 7.62x39 round and the firearms for which it was designed. The 'new' firearms discussed in the report are the AK, SKS, and (apparently) the Stetchkin pistol.
Under the section heading "Seucrity Measures" the report explains how each rifle and every round of ammunition was meticulously accounted for -- with severe punishment resulting should any round go missing.
Given the very high level of security so many years after the end of WW2 as well as the Korean War, it seems pretty safe to say that the SKS did not see action in either conflict.
https://www.cia.gov/readingroom/docs/CIA-RDP82-00046R000500020007-7.pdf
Under the section heading "Seucrity Measures" the report explains how each rifle and every round of ammunition was meticulously accounted for -- with severe punishment resulting should any round go missing.
Given the very high level of security so many years after the end of WW2 as well as the Korean War, it seems pretty safe to say that the SKS did not see action in either conflict.
https://www.cia.gov/readingroom/docs/CIA-RDP82-00046R000500020007-7.pdf