Depending on the oil cooler arrangement, the oil would go through the cooler before going to the bearings, no? I think most of the sandwhich plate setups I have seen show the oil pumping through the cooler before making it's way to the engine.In the pan, as it should be.
That’s what the bearings see.
And one can calculate (with a pretty reasonable degree of accuracy) the temperature drop across their oil cooler if given BTU's, thus, if you know the oil inlet temperature for the cooler, you can come to a reasonable conclusion of the outlet temperature and vice versa.
With that being said, I think there are many places you can put the oil temperature sensor, you just have to adjust your temperature expectations accordingly. IE, 230°F on cooler outlet would potentially be cause for concern (assuming 50°F delta across cooler), whereas 230°F in the pan would not IMO, since the oil in the pan is oil which has not been cooled.