I had ChatGPT explain why this is works as a unlimited hotpot. Very cool: "It works because carriers detect tethering partly by looking at TTL values. Android subtracts 1 from TTL when hotspot/tethering packets are forwarded, so the carrier sees a different TTL and knows the traffic came from a tethered device.
Your eBPF program increments the TTL back by +1, hiding the fact that the packet was forwarded through your phone. So to the carrier, the traffic looks like it originated directly from the phone, not from a tethered device. That defeats one of the carrier’s tethering-detection methods."
in normal you would do use this trick. but however new phones does not include the kernel module that helps you to modify the TTL using iptables