The original beam and the replacing towbar are mounted in the same way.
The link is to the installation instructions for the foldable towbar. I couldn't find the one for the
fixed towbar right now, but as far as the towbar itself is concerned, it is the same.
It seems that Volvo doesn't like to sell the fixed towbar, they make it difficult to find.
https://accessories.volvocars.com/In...XC90(16-)/2019
Scroll down to where the original beam is removed and the towbar installed.
Note the hint "This step is easier with two people". Judging by the weight of the original beam, it is
So I don't think that the towbar affects the way the car will absorb rear impacts.