Yes words mean things. Unlimited means something. It means something that no ISP ever could possibly deliver.
Every ISP is going to reach network capacity at certain times and be required to make a decision about who gets throttled. T-Mobile decides to give a priority to people who have not already transmitted a lot of data. Another ISP may decide to throttle everyone on the network at any given time equally. Or maybe they will just always pre-throttle everyone to the point where they can basically guarantee that everyone can access their data without further throttling
Let's say you have capacity to transmit 6 packets a second. We have 2 customers A, and B that can transfer data at 4 packets a second (pps). If they never try to transfer at the same time, then they can always go at full speed. But what do you do when they want to transfer at the same time?
Fair throttling base don instantaneous rate
Both A and B are throttled to 3 pps whenever they are both transferring.
Fair throttling based on total data sent over time.
Throttle the person who has sent the most data to 2 pps
Let the other person go at 4 pps until they become the heavier user
Throttling based on ensuring consistent quality of service:
Throttle both A and B to 3pps at ALL times, even if they are the only one using the network.
Which one is more fair? It is subjective, but the point is that there is not way to deal with the demand on a network exceeding supply other than limiting the amount of data that some people can get.
None of them are "unlimited". They all employ some type of "throttling" strategy when at network capacity (although Scenario 2 is what is most associated with ISP throttling).
My point is not that T-Mobile is right in advertising "unlimited" data, but that a savvy customer should be skeptical of the term "unlimited data" and find out specifically what this means, because it certainly can't mean getting data any time you want at unlimited speed.
In the case of T-Mobile, I don't even think they ever specify data rates at all other than vague terms like 4G and 3G, which refer vaguely to the generation of network rather than the actual rates. You can have a really slow 4G connection.
You can have a throttled connection on a fast network that's faster than an unthrottled connection on a slower network.
It's not that T-Mobile advertised something and didn't deliver it. It's that they advertised something vague and/or impossible.
People are mad because they have an expectation of how fast/consistent their connection would be and their experience didn't match their expectation. I'm saying that terms like "unlimited" don't do anything to help clarify expectations in any scenario, with or without throttling.
Maybe ISPs could present a standard set of statistics like:
minimum rate, maximum rate, data cap
Gold Plan: min: 1 Mbps, max 15 Mbps, cap = none
Silver Plan: min: 1 Mbps, max 15 Mbps, cap = 2 GB then throttled to min: 0.5 Mbps, max: 1 Mbps, cap: none
Economy Plan: min: 0. 5 Mbps, max 0.5 Mbps, cap = none