Old vs. New
I couldn't help but think about aging your money when I saw this. Enjoy!
If I budget 1/12 of my true expenses every month and I'm living on last month's income, how can I be falling behind on my true expenses?
If you lose your job, classic rule 4 vanishes
It didn't when I lost my job. How you reallocate when money stops arriving is an individual choice. I chose to give up other things before I lost the benefits of budgeting in month sized chunks. In fact, I would intentionally ride the CC float and probably even carry interest-bearing debt before giving up the buffer. (Interest is merely the price of clarity and convenience. I wouldn't pay $100/month, but I'd probably pay $10. Everyone has their own threshold, of course.)
So no, it doesn't vanish unless you make that choice.
Perhaps, and Rule 3 says to correct that as soon as you realize it. Whether that means you unbuffer yourself or you give up something else is a personal choice.
Being buffered is simply another priority that provides value, just like having money in the Rent or Grocery or Vacation category.