This topic has come up repeatedly in the past and I don’t believe that there is a clear, fixed, and permanent answer. If you put the new pair on the rear, then they will be worn little when you rotate them as you should at around 8000 miles when the new pair then goes to the front. By that time the new pair would have been worn more if they were initially used at the front. It might be possible to say that there is only a temporary period of time when new tires are safer on the rear or less safe on the front. If new tires at the rear was overly important, that should be in your owner’s manual and it is not in mine.
With a motorcycle, front and rear tires are dedicated, no issue there. The new tire goes where it is needed.
If a new pair of auto tires had a lower traction rating than the old tires, I might want the new pair on the front.
There may be little difference in traction if the older pair of tires is worn little. If the older pair is nearly worn out, then new on the rear might be safer especially if you replace the older tires before the next rotation. Anti-lock brakes and traction control can make the new tire location of little importance.
New tires on the rear may or may not present a slight, temporary traction advantage for many scenarios and will get you out of the door with less chance of a trial lawyer using whatever means possible to extract money from the tire installer if you should have an accident due to loss of control.