Separating brisket flat

Can't really tell from.the picture but just follow that big fat line from front to back, looks like you hit it perpendicular vs horizontal 

It’s a little hard to tell from the picture but it appears that you did it as well as that brisket would allow.  The big piece looks to be all one lean muscle with the fibers all running in the same direction. That would be the pectoralis major that makes up the majority of a brisket.  The other pieces look quite fatty so they likely contain portions of the pectoralis minor.  It’s fibers should have been oriented at about a 45-60 degree angle to the fibers of the pec major.  Given the pics and your comments about the lack of a fat plane I’d have to guess that this is a select brisket with relatively little fat.