I have a variable boot floor and make good use of it. The benefits as I see them:
1. Segregated storage, all my maintenance nicknacks, walking gear spend roof bars are tucked away out of sight and harm.
2. You get a much more robust floor than the standard boot floor, which is pretty thin and feeble.
3. You have quick access to the stuff that is under the variable boot floor.
It would be great for keeping anything chewable (i.e. Everything) out if reach your dogs, but if you have to install a dog divider then you'd loose that easy access to the stuff stored under the boot floor.