Nothing wrong with mounting a different sized tire as long as it fits on the wheel and doesn't rub on anything. However many people with lifted trucks mount the largest tire they can and live with the rubbing. So trim pieces to reduce the rubbing. You need to make sure the width of the tire is a suitable size for the width of the wheel and it is for the same diameter wheel (assuming you are staying with the same wheel). I have mounted tires many times that are within a 1/2" in diameter as the speedometer is only slightly affected, but you can sometimes get a cheaper tire in a more popular size or have a larger variety to choose from. Check out
https://tiresize.com/calculator/ and you can compare tire sizes. The stock size is a more odd size and has less availability than other sizes.
255/65-16 tire is 29.1" tall, 10" wide (stock)
245/75-16 tire is 30.5 " tall 9.6" wide 4.8% speedo difference. speedo says 60mph actually going 62.9mph
From experience without a lift kit the 245/75-16 will rub when turning. I have the same size dia tire with a 2" lift and the front tires rub on the plastic liner behind the front bumper during sharp turns while parking. 255/70-16 are 30.1" tall (3.4% speedo difference) and will also just barely rub depending on the load in the truck. The 245/70-16 is nearly the same size (29.5", 1.4%) and has a much larger size variety plus no rubbing. The Pathfinder doesn't have huge wheel wells so you can go too big or it will rub.
The Dunlops you are looking at is only available in that one size for a 16" rim. My personal opinion is after Goodyear purchased Dunlop they have changed Dunlops focus to solely performance tires and moved away from truck tires. All of the currently available Dunlop tires for trucks/SUV have very spotty coverage of tire sizes. Goodyear makes all Dunlop tires, made at exactly the same plant on the same machines. Goodyear has a significantly larger availability of tires in the Truck/SUV section.