Fooling you into thinking that a 720p DTV broadcast was actually a UHD HDR program would be an example of a pretty incredible scaler. Come to think of it, fooling your "TV" into thinking the content is HDR is also pretty magical.
You keep claiming I have been fooled, but you aren't here to see and I have no idea what you have other than your references to online information searches. You never state what you are using. All my systems here do 1080p except my older PS3 which is the only way I can display 720p that is detected and displayed in the info panel from my projector. I don't have a 4K TV set. Feeding the Projector with pass through with it's upscaler turned off can display the fuzzy soft image of 720P. The upscaler to 1080p is better.
The AppleTV has settings to output lower SD signal but I haven't looked at those. But a 1080p 24fps upscaled to 2160 24p in the projector looks really good. I've been using this mode to view frame packed 3D and it is sharper and more detailed than native 1080 24p. For broadcast, 1080i or 720p looks good at 2160 60p. But all my UHD content whether disk at 24 fps or internet streaming at 2160 60p using pass through, scaler off, is an obvious step up again.
My projector Sony VPL VW 665ES is a middle priced Sony so it doesn't do the upper end of the video spectrum. It maxes out at 2160 x 3840 60p 4:2:0. with HDR 10 bit or BT2020. The 1000 series cost twice as much will handle the new HDR10+ and 4:4:4. But as I understand the upscaler in the 1000 series is the same as what I have.
HDR is not something that I can claim I have even though the info display detects it because the projector just will not output enough nit brightness to show off what a Laser Projector can achieve. True HDR is said to require a 2000 nit display for the full benefit and Dolby Vision 5 times that. The detection of HDR is by meta data in the transmission. It's not magical. If the image has no range of brightness because that is how it was shot, then HDR is meaningless for what you see. But a scene at night of a camp fire where you can still see detail in the surroundings with details in the flames is where HDR can be of benefit. With my projector, HDR or not is almost no difference. But, 10 bit color over 8 bit is more important. High resolution in UHD definitely is present over a 1080p transmission. A consumer camera with a tiny sensor shooting 4K video will look far worse than a 1080 x 1920 broadcast camera with 3 chips, one for each color. The broadcast camera will upscale to 4K and look better than the consumer 4K camera.
I don't believe in magic. I believe the info display that detects the inbound signal is doing it's job and what I see pleases me. I believe when I select pass through it does the same as if I wire the source to the projector direct. I can be entertained by a "magician" but I know it is just skilled slight of hand trickery.