This is always a given and if you read the tweets and the pages that they point you to you will find what you need to know.
Don't skim read
Also if you read a little more you would have read you use the Droid2 root method to get root back if you lose it.
This is what the tweet looked like (Its the actual tweet from P3)
P3Droid
Okay, you will lose root, make sure you have pushed the rage in the cage info to your phone /data/local so you can reroot...
Is that crystal clear enough?
P3Droid
visit my friends RootzWiki for
droid X (2.2) rooting instructions Droid 2
They don't give you this info for fun.
My update went super easy and I didn't lose root, however it was plainly stated you might and to use the Droid2 root method (see above)
I know it can get a little hard to find crystal clear instruction but if you read the links that are provided by the group releasing the ROM or update you will almost always find all you need.. (follow them not the forum)
Even if you find crystal clear docs there is no guarantee you or anyone will do it correctly and that is why you see all the disclaimers.
Good luck and stop getting pissed, It's not worth it.