Screenshot not working on Apple Watch Series 8 (with solution but also questions)

Not so much a question (because I already found the answer), but more sharing my experience in case it helps others, and if any Apple afficionados are monitoring this forum who might be able to improve the docs, and offer any insight.

In this respect, the guide tells us how to take a screenshot on the watch:

I tried this a million times but couldn't get it to work. The watch would vibrate, and then the phone, which suggested that something was happening, but the screenshot never appeared as promised on the iPhone. I tried disabling and re-enabling the screenshot feature, on both sides, I tried restarting both, I tried updating to latest 16.2 OS on both sides, I tried unpairing and re-pairing. I spent some length of time on a chat to support, then upgraded to a phone chat, then further to a senior support technician, including taking device diagnostics remotely.

In none of these support interactions, and in none of any other forum posts or articles, was it ever suggested what the real problem was (and therefore what the solution is). Nor is it clear from the official guide (linked above).

Basically I was pressing and releasing the two buttons on the Watch in a similar manner to how I do it on the iPhone... press and then release, but not in any particular hurry... quite deliberate, maybe hold for half a second, then release. Just not too long that the power off screen (on the iPhone) comes up.

But using the same method on the Watch... naah. Nothing. Nada. Well, the watch and phone would vibrate, though not every time, so it suggests that maybe I'm doing it right (sometimes) but something doesn't happen after that should?

Purely by chance (when speaking to the senior support technician over a video link to demonstrate what I was doing), I pressed and released the two buttons really quickly, and voila... watch screen flashed, and screenshot appeared on the iPhone.

So the key appears to be to press/release quickly, without holding down even for a short time like you can on the iPhone to take a screenshot.

After all that time trying to figure it out, the solution was easy... very quick press/release... don't dither.

The most frustrating part is that the official guidance (see above) doesn't say this. All it says is "press the Digital Crown and the side button at the same time".. nothing about how quick it needs to be, nothing about releasing quickly (in fact, nothing about releasing at all, but I suppose that's inevitable if we aren't to remain permanently attached to our watch).

Perhaps the docs can be updated to reflect this?

Perhaps this behaviour is new for the Series 8? I asked others with older watches (Series 6 I think) and they can press/hold/release on the watch more slowly and it still works (more like the iPhone) so maybe it's a recent change? Or maybe my own watch is peculiar/faulty? Why does the watch and phone vibrate at all when pressing/holding for longer... what is it doing, if not nothing at all?

Anyway, hope this helps, and any insight from Apple techs or afficionados on this matter would be interesting.