I'm surprised mount doesn't complain about those first 5 lines! Those are not
properly-formed fstab(5) entries.

No, it doesn't. Those entries are ignored except /boot.
One interesting thing: i always had that bunch of malformed fstab entries.
Before the change from static to uuid it looked like this in fstab:

/dev/mmcblk1p1 loader1 vfat defaults 0 0
/dev/mmcblk1p2 reserved1 vfat defaults 0 0
/dev/mmcblk1p3 reserved2 vfat defaults 0 0
/dev/mmcblk1p4 loader2 vfat defaults 0 0
/dev/mmcblk1p5 atf vfat defaults 0 0
/dev/mmcblk1p6 /boot vfat defaults 0 0

Now it looks like wic fails in getting the correct value and uses sda as a best bet

you're proposing (a bunch of malformed fstab(5) entries) should be considered
correct.

I guess i just got used to it because it has always been like this since i build for the rock-pi

In the mean time I'd like to apply your patch 2/2, if you could please add
your SoB line?

Have sent new patches. Just delete the first one if you dont need it