I disagree. 内地is the standard way to refer to eastern parts of China from Xinjiang. You will often see this mis-translated into English as "inner China"--that's a bad translation because "inner" to English speakers implies inland, and Xinjiang is inland relative, say, to Hunan. The nei / wai is a distinctive Chinese division, going back to Qing or before, and Manchu used equivalent terminology. It's a very sino-centric way to consider the territory.