Russell, Keynes, Wittgenstein and Haldane all visited the Soviet Union. Needham spent time in China during the Sino-Japanese War and again after the communist revolution. So some intellectuals had access to first-hand accounts—though I agree that the permission to visit and the experience itself was tightly controlled. There were also lots of Russians and Chinese in exile who intellectuals could talk to.
Russell, Keynes, Wittgenstein and Haldane all visited the Soviet Union. Needham spent time in China during the Sino-Japanese War and again after the communist revolution. So some intellectuals had access to first-hand accounts—though I agree that the permission to visit and the experience itself was tightly controlled. There were also lots of Russians and Chinese in exile who intellectuals could talk to.