Yes, you can't use bitcoin off-the-grid because to conduct bitcoin transaction to need to connect to internet. Bitcoin is a digital currency after all and there is no way you can use bitcoin even if you have the full-node. In fact, the full-node requires internet connection to synchronize with the bitcoin network. To use bitcoin anywhere you are going to need internet connection, period!
Off-grid means without paying for utilities. You can buy a cheap LTE connection and have wireless Internet wherever you want.
It's possible to live like that as long as you pay for the Internet but he could have a house in the mountains with its own water and power.
The problem lies in profitability. Such off-grid system will be expensive and it will take years for it to pay for itself.