'Stage' and 'state' do not mean the same thing, although they are often mistakenly used interchangeably.
Die state is an observation about the age of a die within its production lifespan. EDS dies have crisp features and show little or no flow lining from use. MDS dies still retain most of their sharper detail, but flow lines are clearly present. For Morgans, most examples with strong satin luster are from dies like this. LDS dies show their age, details begin to fade and flow lining becomes pronounced.
Die stage by contrast, note different events within a die's life. These include things like clashes, polishing jobs, gouges or breaks. There can be multiple die stages within a single die state, like we see with the 21-S Thornhead. Taken further, when you consider just one die, there can be multiple marriages within a single die stage, like we see with the A1c reverse and a bunch of rare 78 8TF VAMs.
Flow Lining: During coining, the natural flow of metal is toward the rim. As the die wears, fine lines develop in the fields. If you have a few mint state pieces from a progression, put them side by side and note how the texture of the fields change. You'll see the flow lines.