Structurally, there's no difference in the stress of standing on a specific spot and hanging from it.
NO..that is where you are wrong..
there is little difference in standing on a pipe, than hanging from it with your hands, it will support you or it won't , depends on the size of the pipe
there is a World of difference in standing on a roof
than hanging underneath from two screws .. screwed into 2" truss
the forces involved are much different, and much more concentrated
that is point you are not accepting
standing on top, you are standing on the LUAN aka plywood top surface the roof itself designed to carry weight, it spreads the applied weight across all the truss surfaces it makes contact with
hanging under the ceiling any applied weight is a direct pin point force applied to the lag screws in a 2" truss never meant to have something screwed in and pulling down
its like the difference between hanging from a pipe with both palms/hands gripped tightly around the pipe
or
trying to hang by the thumb and fore finger of each hand
trying to hang your full weight on just (2) digits of each hand is a lot harder, to much force applied to , too small an area
its physics
those 2" trusses where never designed to have heavy lag screws in them and weight hanging from them, use a big enough screw and the truss is going to split even if you hit it dead center
