OK, I haven't run the Surface Diagnostic Toolkit check for updates before (thinking I wanted to be as "pure" with all updates as possible on this SP4, since I tried other Intel drivers and such on my previous one, but they never helped - It was different,
but not better.)
Anyway, running it today, it tells me this:

I haven't let it install these yet, at least partly because what I'm *really* wondering is bunch of other questions driven by this:
If these are really required to make sleep (and other things) work correctly, then why hasn't Microsoft pushed these out through Windows Update already?
Why didn't they go out with the 4/15 or 4/19 updates?
Why was a completely different, non-standard method chosen to deliver these updates? (Some kind of half-vast compromise between Windows Update and the Nine Insider Rings of Hades?)
What good is Win Update if it won't find and install what's really needed for my Surface to work?"
It certainly seems that something like a watchdog timer driver is critical, but that makes its omission from the pushed updates even more of a mystery.
I'd love someone at Microsoft to comment on this (yeah, right...), but I do wonder why these two fixes in particular have been withheld from the great masses yearning to be free from the tyranny of Surface fail. Come to think of it, this situation bears an uncanny resemblance to a (forced re)boot stomping on a Surface Pro Customer's face, forever.*(*The reference is to Orwell's 1984: "But always — do not forget this, Winston — always there will be the intoxication of power, constantly increasing and constantly growing subtler. Always, at every moment, there will be the thrill of victory, the
sensation of trampling on an enemy who is helpless. If you want a picture of the future, imagine a boot stamping on a human face — forever.")
On that note, I have to say that the Surface Pro 4 is still Doubleplusungood, even after the latest round of updates. (And apparently, even with the two updates above applied as well...)