It's not really binary or a spectrum. Royce was not taking about what he observed people doing, but how he believed large software projects should be conducted in the future.
In that, he first introduces what has come to be known as Waterfall. While he considered it to be fundamentally sound, he posits that it carries significant risk and then goes on to tell what needs to be added to diminish the risk. Those additions are what oft get called Agile (although not in the Manifesto sense).
You have a point that "simplification" is more in line with the device he was trying to use, but with the intent of leading you into understanding the more complex aspects of his idea. Kind of like that owl drawing meme where you start with two circles and then draw the rest of the owl. There is only one idea present. In other words, "Waterfall" and "Agile" are the exact same thing, just at different stages of communication.
Where others have tried to invent "Waterfall" as it own distinct thing to contrast with "Agile", it would be fair to characterize that as a strawman. If anything all projects are "Agile" at their core, with varying degrees of deviation happening in a multi-dimensional space.
In that, he first introduces what has come to be known as Waterfall. While he considered it to be fundamentally sound, he posits that it carries significant risk and then goes on to tell what needs to be added to diminish the risk. Those additions are what oft get called Agile (although not in the Manifesto sense).
You have a point that "simplification" is more in line with the device he was trying to use, but with the intent of leading you into understanding the more complex aspects of his idea. Kind of like that owl drawing meme where you start with two circles and then draw the rest of the owl. There is only one idea present. In other words, "Waterfall" and "Agile" are the exact same thing, just at different stages of communication.
Where others have tried to invent "Waterfall" as it own distinct thing to contrast with "Agile", it would be fair to characterize that as a strawman. If anything all projects are "Agile" at their core, with varying degrees of deviation happening in a multi-dimensional space.