Right...a dealer is not going to let a vehicle sleep for 8 hours, so they do the reset with the scan tool.Letting the car sit overnight will allow the BMS to relearn its state of charge. If that's all you want, then a BMS reset isn't necessary.
But that's just one part of the equation.
The BMS also knows the age of the battery and takes it into consideration when choosing the charging strategy. The age counter must be reset when you install a new battery, otherwise the BMS will treat your new battery as if it were old and will charge it accordingly.
I know of instances where some systems (particularly the stop&start, but also the heated steering wheel, or heated windscreen if fitted) had stopped working due to the load shedding caused by a weak battery, and they continued not to work after having the battery replaced. A BMS reset fixed that.
Here's the battery replacement procedure from the service manual.
It doesn't say it's optional. It doesn't say that simply leaving the car parked overnight will do.
I put an AGM battery in my 2011 5.0 F150 and just let the truck sit overnight for 8+ hours per the manual. Been fine for years.