As I mentioned before, I have no axe to grind either way, but my take on it is that your iPhone can only ever receive data at "x" speeds/rates.
For example, in my iPhone I have a Vodafone (UK) SIM and at home for example I get about 2.5Mbps down on any given speed test.
Now, if I were to download at full pelt on my iPhone for an hour I could only download "x" amount of data in that 60 minutes due to the network I'm on and my location.
So, if I were to tether my phone to my iPad and my laptop for example, I am
still only able to download at that same speed for that 60 minutes, so what's the issue (apart from the contract saying that I'm
not allowed to tether)?
Connecting 2 x extra devices to my iPhone's data connection isn't going to magically make Vodafone increase the speeds I get (and therefore increase the amount of data I can receive).
Just my 2p's worth.