Interesting, if in a negative sort of way. I've found lots of threads like this one in various places, and they all end in the same place: bafflement and no solution.
It's over two weeks since I asked Intel, who made the thing and ought to know, and over a week since they asked me for serial number and system details. Silence since then.
There has to be a reason why a variety of (live) SSDs don't function at power-up in a variety of computers, whereas every SATA hard drive I've had does so with no fuss unless it's failed. It seems nobody knows - or the answer is classified.
When I get back from holiday I'll make my little power connector delay device and see if that fixes it. My SSD works fine if the PC is up and running before the SSD is powered on. That suggests to me that something in the SSD BIOS may be very impatient.
We'll see! My curiosity is stimulated.