Fuel consumption (as well as gearbox preservation) is also a factor. Choosing 3rd instead of 2nd in just those corners can save you .1-.2 litres/lap with bugger all effect on pace, help conserve tyres and that can equate to an extra lap or 2 of stint length which is incredibly important in an endurance race.
Although I'm not sure how much gearbox preservation is a factor considering the reliability of factory built off-the-shelf GT race cars.
What's also noteworthy is how often sim-racers bash the limiter even on upshifts vs RL. Just watch all the YouTube videos!
Also power-on exit stability. There are 2 schools of thought on this among race drivers especially in rain. 1 prefer the lower gear that they normally use in the dry, supposedly for better engine response, at the risk of power oversteer. The other prefer a higher gear for less torque output to the rear wheels.
Engine braking effect is conservative in the game. It's not easy to lock the rears on aggressive downshifts and spin. Unless you have reasonably rear-biased brakes like I do where the rears are near the limit and trail-brake+downshift sends the arse end wayward.
Even F1 and LMP1 driver onboard videos show they're late on the downshift to not be near the limiter.