graphvpnquestion bypassing my Mullvad VPN which had local network sharing disabled
No idea how Mullvad or any Android VPN disables local network access. Maybe they are pushing routes for the 3 common internal subnets? In which case can be a bug.
UPDATE: Just confirmed with ProtonVPN, which has a similar "LAN connections" feature. It pushes a bunch of extra routes. Instead of Termux, I used Ping&Net app with Network Info.
Try looking at your routing table with Ping&Net during 3 conditions: No VPN, VPN with local network sharing disable, and again with enabled. Compare the results.