isArray and std.container.Array

["Nordlöw" via Digitalmars-d-learn]

Is there a reason why isArray!T doesn't match T when T is a 
std.container.Array? I'm asking because after looking into 
msgpack-d because of

http://forum.dlang.org/thread/aclapseyptgcwntdavwt@forum.dlang.org#post-aclapseyptgcwntdavwt:40forum.dlang.org

I realized that this is the reason why msgpack doesn't correctly 
pack std.container.Array.