Yes your explanation about buying at a DIP is okay but buying at a DIP is mostly for those who uses the DCA strategy and they have reserved funds that they can use to buy Bitcoin at cheaper price when a DIP occurs.
There was never a time when buying the dip was meant to be for those who DCA. Buying the dip is a pattern of buying and an investor who wish to lump sum or dca can as well buy the dip. Some investors rely on only buying the dip as their strategy without considering dca or any other strategy. Like i said before it all falls down to the individual risks. Buying the dip can seem to be a lot less risky since one has to wait for the bottom to buy, but what those who wait for the dip dont know is that it can be more risky when the dip never comes and they cant buy at all. Waiting for the dip will leave them no other option than to not buy at all. Now imagine that an investor has to sell off his btc for profit and wait to buy a dip that never comes while the market keeps going up is that not a huge loss for him?