They're a bit more binding, smaller, provided by the Rust bitcoin library,
sane, and we don't have to worry about malleability since all of our inputs are
SegWit.
All uses were safe due to addresses being converted to script_pubkeys which
don't embed their network. The only risk of there being an issue is if a
future address spec did embed the net ID into the script_pubkey and that was
moved to.
This resolves the audit note and does offer that tightening.
