Bind outgoing socket connection to specific interface doesn't always work on Windows 11

Question

For a VPN app on a Windows 11 machine I have my regular wifi interface (192.168.3.7) and a Wintun Tunnel interface (configured to have IP 192.168.3.6). The routing tables are set up so that all traffic should go to the Wintun Tunnel by default. However the app still needs to be able to make some connections using the wifi interface. I tried creating a socket and binding it to that interface's IP. On one of my Windows 11 machines that works as expected and the socket's traffic is routed to wifi. But on another machine the traffic is still routed to Wintun. Why doesn't this setup work correctly on both machines? Are there other settings somewhere that affect routing decisions?

Example Python code for how I create the socket and bind it to the wifi interface:

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(("192.168.3.7",0))
sock.connect(("www.google.com",80)) # these TCP packets still get sent to the Wintun Tunnel

And the routing info on the device:

===========================================================================
Interface List
 11...........................Wintun Tunnel
  9...ce 47 40 77 44 bc ......Microsoft Wi-Fi Direct Virtual Adapter
  2...ee 47 40 77 44 bc ......Microsoft Wi-Fi Direct Virtual Adapter #2
  8...cc 47 40 77 44 bc ......Realtek RTL8852BE WiFi 6 802.11ax PCIe Adapter
 18...cc 47 40 77 44 bd ......Bluetooth Device (Personal Area Network)
  1...........................Software Loopback Interface 1
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     192.168.3.1   192.168.3.7     30
          0.0.0.0          0.0.0.0         On-link    192.168.3.6      6
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    331
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    331
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    331
     192.168.3.0    255.255.255.0         On-link    192.168.3.7    286
     192.168.3.0    255.255.255.0         On-link    192.168.3.6    261
   192.168.3.6  255.255.255.255         On-link    192.168.3.6    261
   192.168.3.7  255.255.255.255         On-link    192.168.3.7    286
   192.168.3.255  255.255.255.255         On-link    192.168.3.7    286
   192.168.3.255  255.255.255.255         On-link    192.168.3.6    261
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    331
        224.0.0.0        240.0.0.0         On-link    192.168.3.7    286
        224.0.0.0        240.0.0.0         On-link    192.168.3.6    261
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    331
  255.255.255.255  255.255.255.255         On-link    192.168.3.7    286
  255.255.255.255  255.255.255.255         On-link    192.168.3.6    261
===========================================================================
Persistent Routes:
  None