Mmm
So the Danforth will pull out with wind and tide changes, reasonably sure this won't apply when using the anchor as an emergency brake.
The Danforth is difficult to set, I suspect that this is due to ineptitude. If the anchor is thrown over the side with tens of m of chain and the boat is put in reverse, it is v likely to drag along the seabed, if it is dropped over the bow of a narrowboat heading at 4mph towards a weir, I suspect it will set.
As for the ability to stow flat, derided earlier in the thread,
I would have thought that the ability to be able to store an emergency anchor somewhere handy was highly preferable to some odd shaped thing stuck in a locker somewhere, giver the absence of a dedicated bow roller on most canal boats.