Never heard such nonsense. I've been using Woodleighs since long before they were even bonded, and never had a core seperate. All my mates concur. Its just not possible with the current bonded-core bullet. You can turn them inside-out if you push them fast enough, but they still hold together right to the last millimetre of bullet-shank. I'll toss up a few photos on the weekend, though I would have thought board-members would be sick of seeing pics of perfectly-mushroomed Woodleighs by now!

BTW, the thickened jackets were introduced to cater for the very high velocities becoming trendy in American cartridges (Weatherby .378, WSM, etc). It was a response to over-expansion, NOT core seperation.