When I started brewing, DME was actually what you now refer to as LME.
DME was an acronym for Diastatic Malt Extract made by Edme. and had sufficient diastase to convert a certain amount of starch into sugar. You added the extract to hot water, adjusted the temperature to mashing temperature, and mashed the adjuncts without any need for whole grain which was generally not available.
I have no idea if extracts now have diastase.