Typically they only accept connections from addresses allowed within your tailnet, but there isn’t anything particularly complex about how funnel allows any incoming address.

P2P wireguard connections that is. Funnel needs to accept arbitrary connections.

Further, like most of tailscale’s operations, funnel isn’t requiring them to host or even proxy any significant amount of data, it’s just directing incoming connections on that domain to a device on your tailnet.

And how is that supposed to work without proxies? You can't just point DNS at some device's public IP and then expect everyone to be able to connect to it; that's not how firewalls work. TS IPs aren't routed on the public internet either (100.0.0.0/8 is IANA reserved).

AFAIK the way TS has always worked is that it does its P2P magic to build WG tunnels between devices and then does regular IP over those. IP traffic cannot go between devices otherwise (unless they're on the same network ofc.).

there are some advantages to using tailscale funnel in that your ip will be obfuscated and the traffic will be routed through WireGuard so potentially more secure.

How exactly is your IP going to be obfuscated without proxies? How will traffic be routed through WG without proxies?