Alternative explanation requiring no conspiracy theories: The power of these devices almost doubles year over year (unlike the PC/Mac world where Intel barely shift the needle 5%) in both CPU and GPU. Apple use this headroom in the latest devices but, inevitably, given the linear progression in power, older devices don’t feel as fast. Additionally Apple x.0 releases are rougher than they really ought to be, followed by a period of bug fixes and optimization and that return all devices to something resembling their initial glory. Never quite as fast as their initial release of course but 10.3.3 (the latest release, a month ago) flies on a 5s, a phone released four years prior, and I bet it flies again on the end releases of 11.x. The conspiracy theory just doesn’t stack up.
But go ahead and get the X, we know you will, and tell us the same tired theories next year (we know you will).