If the network suddenly splits into 3 sets of 33, then no future transaction can gain a majority, as 33 votes is always less than the 50 required, thus the ledger in all 3 groups is never appended to.  Those transactions time out and no forks results.

I cant explain it in any simpler terms than this, and if you still believe that there will be forks, well, I dont know what else to write.