Believe it or not, I found a work around.
- After NordVPN has started and split tunneling is on
- open phone link. Note that the connection is "offline".
- Now Open NordVPN Setting and toggle Split Tunneling off
- Switch back to Phone link and it will successfully connect. "Connected"
- Switch back to NordVPN Setting and toggle back Split Tunneling on
- Phone Link remains "connected"
Phone Link will stay connected now, even with Split Tunneling on. You can refresh the connection, send text, launch apps, make phone calls. So far it seems to stay connected even with split tunneling on. Unfortunately, you'll have to toggle split tunneling off/on each time you stop/start the VPN.