Art, true. Very true.
A misuse of the word indeed.
CP, Proper screeding is done during the build (after the DPM) and can be - I believe - 100mm / 4" thick. It's sand and cement, as Art says. A lot of dwellings nowadays use this as a base for the floor (often a "timber" sat over polystyrene sheet arrangement).
You'll be hard-pushed to find many screeders as good as the guy in the video, so often the finish isn't 100% . . . which doesn't matter if timber is being chucked down on top . . . if you want a very good finish (say for vinyl) it's normal to then apply
self-leveling compund.
You basically get two types of this, one that's suited to a thin skim 3mm-12mm (for example) and deep base ones that are suited up to 50mm (per layer) . . . thicker ones often have fibres in to help "knit" them together (imagine fibreglass) but they are all applied in a "liquid" state, whereas screed mix is "solid".
But, yes, you can use self leveling compound in place of screed - you'd need to build the layers up if going up to 100mm but the biggest draw-back is cost. Screed is made from 3 ingredients (sand, cement, water), two of which are cheap (sand and water), the other pretty cheap . . . SLC is expensive and, due to it's higher water content will dry much slower.