The pedestrian airbag was introduced before the Automatic Emergency Braking (AEB) safety function was available. Volvo no longer offers the pedestrian airbag as they found most pedestrian accidents were avoided by the AEB.
The V40 is also a rather old car and is based on an old platform. The XC90 on the other hand was their newest car at the time the Uber deal was made and is based on their latest platform. So it is not unusual that both Uber and Volvo would prefer the XC90 over the V40. Besides, given the newer technology in the XC90 it is quite possible it is better in pedestrian accidents than the V40 (with the safety systems enabled on both).
The V40 is also a rather old car and is based on an old platform. The XC90 on the other hand was their newest car at the time the Uber deal was made and is based on their latest platform. So it is not unusual that both Uber and Volvo would prefer the XC90 over the V40. Besides, given the newer technology in the XC90 it is quite possible it is better in pedestrian accidents than the V40 (with the safety systems enabled on both).