in snow mode the first gear is disengaged.
when my auto changes gears you can not feel the change unless im flogging it.
but even then it would be very rare that i feel the change other than the kick back from power into 2nd.
i drive my auto like a manual and have for the last 25000kms.
when i drive it like a manual (change gears myself) mine most of the time just fishes into 2nd.
but after all i put mine through my gear changes are soft.
maybe in your replacement box someone has installed a shift kit which would make changes rougher and faster.
power mode maxes out rev range but still shouldnt be rough.
id be checking to see if valve body has been modified.
my 2cents worth