First what vehicle are you referring to that has a Device Rating of 2 and a Pilot of 1?
Second forming a persona always involves a device (sans TMs, natch)
A persona is usually based on a commlink, cyberdeck, or rigged vehicle or drone . . .
Third, given that vehicles and drones share a number of rules, I am
inferring that a vehicle's Pilot determines its Data Processing. (I say infer to convey that I am not listing any RAW mechanics that support this, but there's a good chance that it exists. I'm just too tired atm to find it.)
[Devices] also have three ratings: a Device Rating and two of the Matrix attributes, Data Processing and Firewall. For most devices, the Matrix attributes are the
same as the Device Rating.
The Device Rating of a drone is the same as its Pilot Rating, meaning all of its Matrix attributes are equal to the Pilot Rating.
Since the non-TM rigger is forming its persona on the vehicle s/he is jumping into, the matrix attributes will be determined by the vehicle.
As the TM rigger already has a persona and is jumping into the vehicle, the icons merge and use the persona's matrix attributes.
1) DP = 2
2) DP = 5