The ONLY M855-type ammo available from Federal is the ammo that is made by them at Lake City. Federal/ATK took over the contract from Winchester/Olin to operate Lake City for the US military in 2000. The only M855 load made is the military load. Thus, this ammo, when it was produced, was INTENDED to be fully mil-spec M855. However, Federal is new to the high-speed SCRAM loading machines used at Lake City, and in particular, they've had problems getting the sealant right, which according to some Lake City folks is not easy to get right.
While it's true that only Federal would know for sure why this ammo didn't pass Mil-Spec, we know for sure that the XM193 failed due to sealant issues, and otherwise is extremely reliable. I would assume (at the usual risk) that this will be true of the XM855 as well. If you are in any way uncomfortable, then follow the advice given and use it only for training/range use. I wouldn't recommend using M855 as a duty load anyway, due to its overall poor performance.
-Troy