You can do this in a GeometryWrangle into the third input of the Vellum Solver, with the group set to “broken”, and code of
i@disableself = 2;. Setting that flag to 2 will disable self collisions for a point until it is no longer self-colliding, at which time it gets reset to zero. (You can set it to 1 to permanently disable self-collisions.) This gives a much smoother tear in this case, as does setting Breaking Frequency to Per Substep on the Advanced tab of the Vellum Solver.
(Note this only works for DOPs-based Vellum setups, since the third input is not exposed in the Vellum Solver SOP, and the “broken” group is only set for that third input.)