Upscale 1080p to 4k

It is 4k upscaled but not native 4k. The main difference being that the Xbox One S takes a 1080p(or lower) image and upscales the resolution to appear in 4k while the Xbox One X is capable of playing some games directly in 4k resolution. Upscaled 4k is has
a sharper image that 1080p but is still a little less detailed that native 4k.

So yes, while you are seeing a 4k image when possible, it is not true 4k.

To Chanogram: this makes no sense, so games are upscaled to 4K from 1080p but movies that are 1080p are not upscaled as well? What a blind spot. All should be upscaled. Makes absolutely 0 sense to have a program to upscale 1080p games ( though I heard
most Xbox one games run at 720p) but that same program cannot upscale 1080p movies to 4K? As I said in another thread, this $400 Xbox should have the upscale capabilities of any $100 upscaling blu-Ray player and it should stream all of netflix's UHD content.
It does neither. Wah wah.

also, Netflix doesn't stream 4K on the Xbox One S. I checked, Flight of the Butterflies is a 4K title but only says HD on the title page when viewed on the Xbox One S. My tv's Netflix app lists it as 4K.

Xbox One S is not really a 4K console,

4K Media Content - Yes

You can play 4K Blu-ray DVD's or Streaming services like Netflix in 4K just fine if your paying the the 4K subscription options,

4K Gaming Content - No

As for games, it only plays games at 1080p but it is upscaled to 4K, other wise a 1080p image without upscaling to 4K, will look much worst on a 4K screen than what it would do, if it was only displayed on a 1080p screen,

A 1080p image upscaled on a 4K screen does look a little better than a 1080p image on a 1080p screen, but it still a 1080p image made to fit a 4K resolution screen, which is what the Xbox One S does

Xbox One X is a 4K console,

4K Media - Yes

4K Gaming - Yes

The issues is not the TV, it's the Xbox One S not being an Xbox One X.

So 1080p is better than 4k upscale?

It will not upscale to 4K as your TV is only capable of 1080p. However your Xbox One X will downscale 4k to 1080p which looks a lot nicer then normal 1080p.