No, it didn't. I had thought of that and checked it
One of the good folks on the xbmc.org forums suggested disabling "Wake on LAN", another also suggested disabling "UEFI boot" (i.e., force legacy boot).
I tried setting both those options last night and voila! I have IR signal coming through to the OS! Well, from several remotes anyway. So now I can keymap the remotes I want to use...
Now here's an interesting one. I've tried TEN remotes - one of those is a universal and sends ten remote's worth of signals in itself (so theoretically it's NINETEEN remotes). And exactly one of them causes power-on to trigger (FYI one of the universal remote options).
Anyone have any theories on that one?!?