This seems like it should be a no brainer that this would be the result. For all intents and purposes the only real difference between the 9070 and the 9070 XT is power and clocks. Now, at an individual card and manufacturer level there could be other differences in the power delivery circuitry and other card components that could make the 9070 xt a more robust card and the 9070 less reliable at the higher frequencies and power levels, not to mention cooling.
That said, the $50 difference and the cost to make custom items argues that most manufacturers are going to use common items between the cards they produce and it might really be that the only real difference is the bios on the board.
I would argue availability/price should be the driving factor in whether to use this method or not. If you need the 9070 XT performance but none are available or the XT price is significantly elevated vs the non-XT version, only then would the risk vs reward be reasonable.