Could be nice to have a check to ensure swap contains ".eli" or ".bde" per https://docs-archive.freebsd.org/doc/13.0-RELEASE/usr/local/share/doc/freebsd/en/books/handbook/swap-encrypting.html
That's the default setting on other BSDs:
- since 2005 for OpenBSD, see https://marc.info/?l=openbsd-cvs&m=111185331505174&w=2
- more recently for NetBSD, see https://mail-index.netbsd.org/source-changes/2021/06/03/msg129982.html