For the most part I agree with you about attaining " full expansion" but here's an interesting example.
A friend borrowed my 300WSM with 130gr TTSX @3500fps to shoot a big black bear, well over 6 ft. The bear was uphill, and standing looking at us. Normally I'm not a big fan of this shot but the range was close and it appeared the bear was going to check us out and hurriedly depart.
The shot hit the chest just under the neck, knocked the bear down. A follow up broadside shot finished it.
Upon dissection and skinning it was found that the first bullet hit the top of the chest/ breastplate area, travelled through and hit the spine where it traveled up the neck, and finally got stuck against a jaw bone.
The bullet was just a tiny shank and smooth expanded front, almost pancake flat. So while most times you see fully expanded Barnes that look like the ads, or maybe the shank without petals, in this case high velocity (and hitting lots of heavy bone at a funny angle) DID cause greater expansion.