The current POSIX.1-202x draft was used as source material. The source of `tty_set_winsize()` and of `tty_signal_pgrp()` in sys/kern/tty.c was used as justification for the line in the DESCRIPTION section pertaining to `SIGWINCH`. However, it should be noted that the `pgsignal(tp->t_pgrp, sig, 1, &ksi);` call in the definition of `tty_signal_pgrp()` only sends the signal to those members of the foreground process group that have a controlling terminal.
Corresponding Bugzilla entry: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=251868
If this patch is accepted, then please use "soumendraganguly AT gmail DOTCOM" for submitter email address in the commit.