initramfs busybox mount / ro then udev remount?

[turtles]

Setting up a initramfs on a new install today and I have a question
Why does root need to be mounted in the initramfs:
mount -o ro ?
and then remounted rw by udev?
and how do I debug this process?
The boot completes (kernel loads initramfs gets loaded hands off to init)
but then after login I am dumped into a readonly root
udev does not remount my root?

I set this up about a year ago on a different box and did not need to include a root (/) in fstab
it gets added to mtab and the init script has the same line starting with