The are two different tire size designations. Back in the old days
truck and SUV tires were designated in LT (light truck) sizes i.e. 31x10.5x15 and passenger vehicles in P-metric 265/74-15. Then LT-metric were introduced by manufacturers, probably in response to globalization and use of the metric system in most of the globe.
As long as the tires are LT rated it does not matter which one you use.