Chord Dave Replacement

I’d imagine that upscaling refers to increasing bit-depth (like from 16 to 24 bits) which adds "vertical" resolution to the waveform... in theory, improving amplitude resolution... making subtle low-level detail more natural and audible (among other things) if done correctly.

Whereas upsampling likely refers to increasing sampling rate (like from 44.1 to 88.2 kHz) which also adds resolution but in the time-domain (or horizontal resolution of the waveform). I’m not sure if there are algorithms that can add high-frequency information that wasn’t captured in the original sampled result... but who knows... maybe so as AI and pattern-recognition software improves.

Also, in conjunction with upscaling, having more sample points could also serve to increase resolution because a bit-word needs to be calculated and saved for each new sample... and the upsampler/scaler might do a more accurate job of this than the typical "oversampling" filter in most DACs. Some DACs may also sound better in terms of being less affected by jitter if they are converting higher sampling rates. I’m just throwing out various ways that adding new samples could improve, or at least change, the perceived sound quality we hear.

"I’m not sure if there are algorithms that can add high-frequency information that wasn’t captured in the original sampled result"

This is the most important statement , I believe upscaling or upsampling whatever you choose to call it is not more than a voodoo.
You can't add information that is not exist at the original recording it's not more than a manipulation process that might degrade the sound. 

That statement makes sense in an analog paradigm. But digital, potentially, can change things.

Think of video. Upscaling an image (well) can most certainly improve the quality. That’s not to say that algorithms can restore *the same* detail that was originally present but lost in the lower-resolution digital capture. However, it can appear to be more like the original to our perception.

This is because scaling is now more sophisticated that merely "averaging new dots between the old" (what used to happen). Sony has had AI tools analyze millions of images in high resolution, and compare with the low-resolution rendering. Based on patterns, the AI learns to "restore" back detail in the low resolution images that appears to our senses to be real detail. It technically isn’t 100% accurate to the detail that was there in real-life, but it’s "more accurate", or at least it appears to be so to our vision, than the low resolution signal. And what’s especially impressive is that they can do all of this on an affordable chip, and in real-time, in their higher-end TVs and projectors.

Upscaling (and potentially upsampling) audio signals is exactly the same. There’s no reason why good AI couldn’t be trained with pattern recognition over time to perceptively restore natural detail into low-resolution digital audio the same way.