I don't know about the WBY stocks being prone to split, but I do know that a Mauser stock that crack behind the tang was stocked by someone who didn't know what he was doing!

Anyone who has ever done much custom stock work, knows the wood is always releaved behind the top tang on a Mauser! I have 10 or 12 Mauser rifles that I stocked, and have stocked about 50 others. Of the ones I have now the smallest chambering is 7mm mag, and the largest is a 458 LOTT,and none of these or the other 50 have ever cracked the stock anyplace! Maybe I'm just lucky, what cha think?