what i said about running from RAM was about completely running from RAM and not needing the boot medium any longer in other words it means you can remove the DVD, or USB from your computer by disconnecting them and continue using the OS like puppy linux
what you say is a different thing. it still needs the boot medium to operate so you can't remove it and about HDD drives, it is like this on all linux distros that i have seen (although i am not a linux expert and may be wrong) but they do not auto mount anything unless you choose to.
the difference in TAILS is that they removed the easy mount but it is still possible to mount the drives.
also the part about RAM is this:
"Tails is configured with special care to not use the computer's hard-disks, even if there is some swap space on them. The only storage space used by Tails is in RAM, which is automatically erased when the computer shuts down."