I would imagine that the shank is what exited like you said, and the front of the bullet blew up early. From what I've shot the Accubond will act very similar as it will open fast but the front doesn't blow because it is bonded it just peals back fast then goes into normal mushroom mode from there. TTSX opens fast also from what little I've shot with them in my 270 WSM and then augers thorough them, I much more prefer how the TTSX performs over the TSX. The Bergers go in and slow blow into the core of the animal and the jacket exits, at least under 400yrds on heavy game and on small deer it goes in and blows a hole out the of side you can reach though.
The Accubond seems to be a go to bullet for the 270 WSM, it's rugged enough to handle the higher velocities yet opens good and accuracy is phenomenal!
Good shooting, and still no pics