I've read through all the discussions on bugs and mailing lists.  I don't quite understand the "Debian gets two mounts; Ubuntu gets one" behavior/situation, but with that posited the rest of the analysis does seem to follow.

stirling: ~$ multipass launch daily:kinetic
Launched: meteoric-mudfish    
stirling: ~$ multipass exec meteoric-mudfish -- /bin/bash
To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.
ubuntu@meteoric-mudfish:~$ sudo -s


## Vanilla VM:
root@meteoric-mudfish:/home/ubuntu# mount -t rpc_pipefs
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)



## With PPA installed:
root@meteoric-mudfish:/home/ubuntu# sudo add-apt-repository ppa:ahasenack/nfs-utils-generator
...
root@meteoric-mudfish:/home/ubuntu# apt-get update; apt-get full-upgrade
...
root@meteoric-mudfish:/home/ubuntu# umount /var/lib/nfs/rpc_pipefs
root@meteoric-mudfish:/home/ubuntu# mount -t rpc_pipefs
root@meteoric-mudfish:/home/ubuntu# mount | grep pipefs
root@meteoric-mudfish:/home/ubuntu# ls /run
NetworkManager  dmeventd-client  needrestart        snapd.socket
agetty.reload   dmeventd-server  netns              sshd
autofs-running  fsck             network            sshd.pid
autofs.pid      initctl          rpcbind            sudo
blkid           initramfs        rpcbind.lock       systemd
cloud-init      lock             rpcbind.sock       tmpfiles.d
console-setup   log              screen             udev
credentials     lvm              sendsigs.omit.d    udisks2
crond.pid       machine-id       shm                user
crond.reboot    motd.dynamic     sm-notify.pid      utmp
cryptsetup      mount            snapd              uuidd
dbus            multipathd.pid   snapd-snap.socket
root@meteoric-mudfish:/home/ubuntu# reboot
...

Broadcast message from root@meteoric-mudfish on pts/1 (Fri 2022-07-22 16:14:14 PDT):

The system is going down for reboot NOW!

root@meteoric-mudfish:/home/ubuntu# stirling: ~$ multipass exec meteoric-mudfish -- /bin/bash
                                                                                                                                                                                                                     ubuntu@meteoric-mudfish:~$ mount -t rpc_pipefs
sunrpc on /run/rpc_pipefs type rpc_pipefs (rw,relatime)
ubuntu@meteoric-mudfish:~$ 

ubuntu@meteoric-mudfish:~$ ls /run
NetworkManager  dmeventd-client  network            sshd
agetty.reload   dmeventd-server  rpc_pipefs         sshd.pid
autofs-running  fsck             rpcbind            sudo
autofs.pid      initctl          rpcbind.lock       systemd
blkid           initramfs        rpcbind.sock       tmpfiles.d
cloud-init      lock             screen             udev
console-setup   log              sendsigs.omit.d    udisks2
credentials     lvm              shm                user
crond.pid       motd.dynamic     sm-notify.pid      utmp
crond.reboot    mount            snapd              uuidd
cryptsetup      multipathd.pid   snapd-snap.socket
dbus            netns            snapd.socket



I agree with your assessment to just get it into kinetic for testing for now.  Ideally, would be good to see a fix land in Debian and/or upstream before we consider doing an SRU just in case they end up refining the fix further.