So I was seeing graphical glitches, freezes and Activity Monitor indicated memory pressure. Turns out macOS doesn't mount a swap file, as I am running from an external SSD install.
This is easily fixed. I can't believe it is a problem though.
By the way I had to change the end of line 4 (because the command in the Ask Different answer returned multiple results) to:
VM_VOLUME=$(/usr/sbin/diskutil list | grep "VM" | awk 'NR==1{print $7;exit }')
It's easy to add the launch item using Lingon X and start it with sudo ./mountvm.sh for the current session.