A little question about safe mode

Hello there.
I have problem here, and don't know if it's bug or "feature" :)
If I prerare boot media (hdd, sd card,usb, etc) with FreeBSD, and NOT
create there fstab, I see such behavior:

1. I need enter manually where from mount root (e.g. ufs:ada0s1a or
ufs:ada0s1a rw)
2. If I enter ufs:ada0s1a rw - I have / mounted in read-only anyway. <== Is
this bug?...
3. If I try to make it rw, with commands
mount -o rw -u /dev/ada0s1a /
there is no errors, but root is still RO.
4. I can't umount / remount some elsewhere this disk, just to create fstab
 (it's already mounted and can't be updated).

So, is this as-by-design, that you need "any other" media to boot, just to
create fstab, or there is "rw" mode broken, or I just missed something?

It's very disappointing to be able boot interactively into system, but have
no way to "fix" fstab to make it non-interactively bootable :)
Thanks.

-- 
Regards,
Alexander Yerenkow