It Depends...
Of course a Fortress CAN
work as a efficient stern anchor. If it is a good idea, depends on the local situation.
How close to shore are you gong to be? Will you have room for a reasonable
scope? In most cases where people are tying a stern line to shore, the shore is very steep, which means rocky, which means your Fortress will be "less than efficient."
In MOST cases, in MOST
anchorages, doing what everybody else does is the most neighborly thing to do. It just means you fit in with the way other
boats are sitting.
I am not saying you should, or should not use an anchor instead of a shore tie. Evaluate the local situation and decide. In other words, use good seamanship, and don't make a decision about how to anchor thousands of miles away.
Certainly if running a line to shore, a floating line is nice to have, but not needed. A "reel" is even less of a requirement. Just tie on the bitter end, and flake out the line on
deck, or in the
dinghy, whatever works best for you. If you run the line in a big loop back to the
boat, any hassle on tying up is more than offset by ease of departure.