So yeah I play X360 & XBONE and want to get the DLC to play on both do I have to buy it on each console or does it stay and carry over to each?
Just like the page says, it will only carry over if you buy the season pass. Buy the Season Pass and it will carry over.
To assume if you buy the maps separately for it to work is just that, your assumptions. If you are not buying the Season Pass then the answer is no.
If the ad says buy a Big Mac and get free fries why would you expect free fries if you bought a Whopper ?