Don’t forget that any rescaling will change the impression of “sharpness” (edge contrast). That’s perhaps why you didn’t agree with the assessment of the editor when watching the video.
And what’s most usually called “sharpness” is ‘edge contrast’ (acuity), not separation between details. An image with a lot of fine, but low contrast, details can appear less sharp than an image with coarser details with higher contrast.
Then, the ideal amount of sharpening is also a matter of taste…
To get back to the original question: the sharpen module implements unsharp masking, which is a fast method to increase acuity. The downside of this method is that it can give halos at strong settings (high radius/high amount).