May be PAF is thinking of VTOL, because it's a derivative of china carrier based 5th gen proposed fighter. For me That's the best case scenario for this.I will be very interested to know why the VTOL is being pursued.
Given We're not in an A/C Carrier Mood & I don't think Fighter Jet Landings could be an Issue since PAF continuously repeats the Motorway drill Exercises.
Only two reasons are coming into my mind atm.
1) It is strictly for the take off purposes. Assuming a situation where the enemy has damaged the tracks and it is unable to fly-off in such conditions. This might be a very handy feature to carry.
2) Second is me just just thinking of a tactic. But it could be possible that the VTOL ability can be used to hide the Figher Jets kind of in a like "Underground Facility" with a small radar on top of the "Underground Facility " in a disguise. If the enemy fighter jet passes through that area and the radar detects it, They could automatically open the facility, use the VTOL for the take of & "Already" You're eyeing the tail of the opponent, giving a very big advantage in dog-fighting perspective. This could work very well close to border, where like Indian breaching after the "Pulwama Fiasco" into the "Balakot Event" where they entered only for a few seconds, but in this case, it could give huge advantage especially if PAF caught them while in a turning back state.