I have been wrestling with these container issues for myself.

There is always a risk in using equipment designed for one
purpose, but put to another. I would not trust cans for more
than an occasional use at low boiling temperatures.

Maybe you should broaden your survival training and show
how to boil water in a shallow container, in addition to
a hanging billy. Thrift stores and cheap retail outlets are
full of containers, made for high temperature cooking.

Though I prefer a deep billy, a shallow container can be
packed so it is safer, in the event of a fall. This can be
relevant in hilly country, or if on horseback.