Walter, you guys have been lucky so far, because it WILL happen. I probably do way more stratux testing than you guys and have been involved with UNIX/Linux (and other variants) since 1977. Without proper shutdown, you are going to have corrupt filesystems. It may only be the very last file the system was writing to (which still allows boot), or in worst case the OS innards / filesystem become corrupt and then the SD card is useless.
I don't understand why so many are so adamant about being lackadiasical regarding file system integrity. Yes, ext4 can fix a lot of errors upon next boot with fsck, but it can't fix everything. That's when the SD card is useless, and of course, it will happen when you're on a long, cross-country, in territory you're unfamiliar with, and you have no backup SD card with you.
It's a simple thing to do, the graceful shutdown and takes maybe 5 seconds.
It's your plane, your life, your equipment. Just don't blame US when you screw up and the disc is unrecoverable and you have no backups, even in the office. Winblows is the same way about not flushing cache immediately, but even if all OS's flushed right away, when power is removed during filesystem header writes, it's gonna go blooey.
If you've never been mugged, does that mean you are safe to walk anywhere in any city without regard?
It will happen to you, and usually at the very worst possible time and location.