Why couldn't they engineer Target Display Mode in a 5k 27 inch Apple Silicon iMac? The Studio Display is basically an iOS computer that acts like a display. Why couldn't they do the same thing with the same cable off a new device?
Well, they couldn't do it in the original 5k iMac because, at the time, there was no standard connection that could do 5k over a single cable (at least, not widely adopted - I think DP 1.3 had only just been announced).
I guess with the advent of TB3 that reason went away after 2017 - but there's no reason to believe that it would be a trivial thing to engineer. Plus, power consumption is becoming an issue, and its not ideal to need a whole iMac running just for a display...
NB: most high-end displays are "computers that act like displays" just like your external SSD drives are "computers that act like hard drives" - people are getting all bent out of shape because Apple has used iOS (or, at least, something with the same kernel version number) and an A-series chip rather than some 3rd party microcontroller and embedded OS.
I think 5K was created for the purpose of pixel per pixel display of 4K content on a 5K display.
Sure, but if I wanted to preview a 4k image in such detail that scaling artefacts would matter, I wouldn't want the distraction of controls and palettes so I'd full-screen it anyway. For video editing on a desktop, if you're not in the super-expensive reference display league (which rules out the iMac anyway) the obvious solution seems to be an OLED or other 4k/HDR TV as a second display primarily for full-screen preview.
Anyway - people also edit 4k content on PCs and
that market has already spoken. 5k displays for PCs launched around the time of the original 5k iMac and sank like a stone. Even here, the main argument for 5k vs. 4k seems to be based on the greatly exaggerated belief that running MacOS in 4k means you'll see horrible scaling artefacts (well, yes, if you climb on the desk with a magnifying glass).
In some workplaces like Healthcare, people do use laptops but the main computing is done on a desktop. I'm not disputing the article but to make a general statement about the workplace eh industry is a bit overreaching. Laptops do have their place as the quote from the article states but the mother load is still the desktop.
Sure, but unfortunately for Apple, that "mother lode" is, likely, mainly composed of commodity PC boxes from HP (#2), Dell (#3) and 101 smaller companies making generic PC boxes for the corporate markets - (Lenovo is #1 but remember, they got into the game by buying IBMs last profitable computer line - the ThinkPad
laptop). Apple have never really gone after the corporate/government/healthcare under-the-desktop market - and for a long time their strong point has been laptops and (more lately) phones & tablets.
...and anyway, the point is about the overall
trend from desktops to laptops which isn't changed by a handful of exceptions. Apple has accelerated that with Apple Silicon, which largely removes any
performance advantage of mid-range desktops over laptops (which now have exactly the same processors). Meanwhile, as internet connectivity improves the "heavy lifting" has started to shift from desktop workstations back to the datacenter or the cloud.