  Soft factorization has been shown to hold to sub-leading order in QED and to
sub-sub-leading order in perturbative quantum gravity, with various loop and
non-universal corrections that can be found. Here we show that all terms
factorizing at tree level can be uniquely identified as boundary terms that
exist already in the classical expressions for the electric current and stress
tensor of a point particle. Further, we show that one cannot uniquely identify
such boundary terms beyond the sub-leading or sub-sub-leading orders
respectively, providing evidence that the "universality" of the tree level soft
factor only holds to these orders. Finally, we show that these boundary terms
factor out of all tree level amplitudes as expected, in a theory where
gravitons couple to a scalar field.
