This is correct. I pay for the unlimited plan with Verizon, but it only has 5GB of hotspot data. I use an iptables
rule to increment the TTL by one, giving me unlimited data on my laptop.
T-Mobile used to work the same way when I used it back in 2016.
iptables
on my laptop (not tethered, but using the phone’s wifi hotspot). I don’t even have a jailbroken android phone anymore because my banking app stopped working on custom ROMs and fighting with it wasn’t a good use of my time.