Dang, started a reply and lost it; I apologize, my hand has been giving me a lot of problems and my typing has been very slow and laborious and my postings have suffered from it; I don't mean to be reclusive. It's a long and slow healing process and you take one step forward and two steps back. The brain finds new pathways around the dead areas from the strokes but it causes anomalies doing it.
Years ago (50's, 60's) most merchandising with chucks was 'stab'n'slab'em' - slice off the steaks and roasts, bone out the neck, cut the shoulder into a boston or cross rib roast and short arm roast and do up the trim, that was all there was to it.
Today, everything is 'muscle-boned' on a chuck; separating out each muscle group to make 'value-added' merchandised cuts (that's a nice way of saying you're going to charge more for the same piece of meat to make more profit).
Here's where the flat iron steak comes from and how it is supposed to be merchandised properly, which shows removing the grizzly membrane. From the small end of the top blade the center membrane is minimal; at the large end it it thick and sinewy.
This is from a post I did on Beef Animations: http://www.smokingmeatforums.com/forum/thread/107516/beef-animations
That is the way the top blade steak is supposed to be merchandised, but as you can see, it is not done; much faster to slice it whole and leave the membrane inside and let the customer deal with it. Hence, the steaks as shown; center grizzle and all.
I am working on finding more animations / demonstrational videos to post; just did one for porcine myology, and will continue to find more to show where the cuts some from.