To answer your question:
Per Wikipeda as to the USMA, “The Class of 1943 was redesignated the Class of January 1943 and graduated six months early. Subsequent classes, from June 1943 through 1947, graduated in three years.”
Correct. Additionally, I believe at least some of those shortened classes returned post-war to complete the curriculum. There’s a photo of a review from that period with part of the Corps in Army Class As, because they were commissioned officers and no longer cadets.