I only string crosses at different tensions when stringing poly hybrids and that is because the poly is naturally stiffer than natural gut.
For full poly beds I string at a uniform tension. My racquet heads remain uniform in shape.
Interestingly, I did buy a PT630 a little while back where the crosses were strung at 2lb tighter and the shape was extended. Once I cut them out, it returned to its normal shape within an hour.