I do have a preference for milestone/session based leveling but it's hard to implement in a cRPG the GM can't be at every session for. .
I do as well and no, it's not particularly hard to do either.
In fact, some of my all time favorites (Vampire Bloodlines come to mind) are computer games that used precisely a goal-based exp system.
Still, this has virtually nothing to do with having the systemic option to question the dead with a spell.
As already pointed the OP is conflating two different issues (having an exp reward system that let you leverage a murderhobo approach for maximum benefit and being able to interrogate corpses) and mistakenly assuming one thing is the cause for the other, when that's just not true.