However, day traders also use the same idea of dollar cost averaging when entering into a particular trade, even if they may enter all within some minutes. They will enter with some percentage of their portfolio then go with another percentage and continue until they meet the hundred percent they want to trade. And when selling too, many of them sell based on the same process because of the volatility of the market.
I think what you are trying to explain in trading is called martingale with what you have said but dollar cost averaging (DCA) is a term used for those who want to hodl. Although it may take same process but they are not for same purpose. The purpose of DCA is usually for longer duration or at least to hodl to sell at a later date but martingale is at the process for sell or buy while the trade is going on in spots. So they are of different classification, one is for hodling and the other is for trading.