4K resolution
The term "2160p" could be applied to any format with a height of 2160 pixels, but it is most commonly used in reference to the 4K UHDTV resolution of 38402160 due to its association with the well-known 720p and 1080p HDTV formats. Although 38402160 is both a 4K resolution and a 2160p resolution, these terms cannot always be used interchangeably since not all 4K resolutions are 2160 pixels tall, and not all 2160p resolutions are ≈4000 pixels wide. However, some companies have begun using the term "4K" to describe devices with support for a 2160p resolution, even if it is not close to 4000 pixels wide. For example, many "4K" dash cams only support a resolution of 28802160 (4∶3); although this is a 2160p resolution, it is not a 4K resolution. Samsung also released a 51202160 (64∶27) TV, but marketed it as a "4K" TV despite its 5K-class resolution.
4K resolution
The 4K UHD standard doesn't specify how large the pixels are, so a 4K UHD projector (Optoma, BenQ, Dell, et al.) counts because these projectors have a 2718×1528 pixel structure. Those projectors process the true 4K of data and project it with overlapping pixels, which is what pixel shifting is. Unfortunately, each of those pixels is far larger: each one has 50% more area than true 4K. Pixel shifting projectors project a pixel, shift it up to the right, by a half diameter, and project it again, with modified data, but that second pixel overlaps the first.