If you want Packed RBDs to grow over time, you need to do two things: scale up the transform intrinsic attribute, and force the solver to recalculate collision geometry.
You can do all this in a Geometry Wrangle or POP Wrangle, it's faster than a SOP Solver.
matrix3 xf = primintrinsic(0, "transform", @ptnum);
scale(xf, 1.02);
setprimintrinsic(0, "transform", @ptnum, xf);
i@id = -1; // force collision recompute