That is attempting to cover how the FTCA partially removes that soveriegn immunity.
It is under that act that the 80+ current suits over this incident were launched.
The problem you have with the Feres doctrine plugging the hole created by the FTCA is that it is always being challenged and each time more ifs and buts are added to the rulings and ifs and buts build up.

If you can't poke fun of yourself, who else are you going to pick on? McBee is the exception though.

if ands or buts are the meat and potatoes of lawyers. the neat little fraternity that continue to remain that or grow up to become judges and/or our favorite parasite, the politician....

Which is why the supreme court says the politicians need to write those laws again so it is clearer when and where the limited soveriegn immunity can be applied and when it isn't so the cases don't have to go through all the expense of going through all the courts before ending up in the top one.