Ok, I've now tried it a few times on my player. If I pull power whilst the disks are spun up then I don't see the "The quick brown fox" message. I have two disks and 64MB of memory so it takes a while to fill the cache after boot, and the drives can sap power, so this isn't completely unexpected. If I wait for the disks to spin down and then pull power I usually see some of the message. I don't have those two final "Powerfail is now..." messages that you don't. but if I understand you correctly then your player is in Standby after boot (which you can't change until we resolve this flash save issue), and these messages occur when you come out of Standby. The kernel code supports this behaviour.

So, you need to repeat the experiment a couple of times ensuring that the disk is spun down before pulling power. If the results don't change then don't bother posting a complete log, just let us know.

Assuming that they don't change then it is probable that the message is not getting sent. There are two possibilities that I see for this. First is that the kernel is attempting to write the flash but never gets done, and second is that the kernel isn't even trying (not seeing power fail).

Where from here? You could look at the GPIO pins on the CPU I suppose. GP0 (pin 86) is the POWERFAIL input. It's monitored for transitions not levels. I dare say that a proficient electronic tech could find a way to safely manipulate that pin so we could see if the kernel picks it up.
You could also scope the FLASHWE pin (output, Flash write enable). That's GP20, pin 60.