I was able to successfully install Steam via PlayOnLinux. I can launch Steam, browse the store, see my library, etc. After I did that step, I followed these instructions to create a symlink from PlayOnLinux steamapps to Windows steamapps:
https://developer.valvesoftware.com/wiki/Steam_under_Linux#Save_space_on_dual-boot_machines
Since those instructions are for Wine, I had to change the command a bit for PlayOnLinux:
cd "/home/dave/.PlayOnLinux/wineprefix/Steam/drive_c/Program Files/Steam"
mv steamapps steamapps.bak
ln -s "/host/Program Files (x86)/Steam/steamapps" steamapps
My question is: now that I've created the symlink, should my games appear as installed in my library on Steam? Because they aren't... I thought the whole point of this step was to make Steam see the games already installed and not ask to download them again.