I think what they mean is that the manpage you link is just synopsis of command line options and not anything that help understand what happens with QEMU and how to fix it when something goes wrong.

I've got several man pages for qemu (FreeBSD 13.0, qemu-5.0.1)

   $ apropos qemu
   qemu(1) - QEMU User Documentation
   qemu-img(1) - QEMU disk image utility
   vdeq, vdekvm, vdeqemu(1) - Virtual Distributed Ethernet wrapper for QEMU/KVM virtual machines
   qemu-block-drivers(7) - QEMU block drivers reference
   qemu-cpu-models(7) - QEMU CPU Models
   qemu-ga-ref(7) - QEMU Guest Agent Protocol Reference
   qemu-qmp-ref(7) - QEMU QMP Reference Manual
   qemu-ga(8) - QEMU Guest Agent
   qemu-nbd(8) - QEMU Disk Network Block Device Server

OTOH, there's no manpage for qemu-system-X, so maybe that's the confusion.

Also, >the pw man page is much scarier than NetBSD’s useradd.

FreeBSD has an adduser(8), which is a bit more friendly than pw.

>which is a bit more friendly than pw.

pw is one of those that i wish had a --dryrun type option enabled by default and required a --doit switch. this was brought up a few days ago, and i really like the idea of scary commands using the dry run as a default.