There's already a term for what you describe - that's a soft-cap. There's also a term for the other thing you describe - unshaped. The product under discussion doesn't have a soft-cap. It only stipulates if you abuse the crap out of the resources, you will be politely asked to leave. It says "unlimited traffic". The traffic is not limited. The unit of measure of internet traffic is the kilobyte. If someone asks you "how much traffic did you use?", you would say "last month? 77 gigs!", and not "77gigs at a rate of 192kbit from 8am-8pm, and 10mbit from 8pm-8am".
There is not a limit on that kilobyte number. Hence the traffic is unlimited. It does not promise "unlimited bandwidth" or "unlimited speeds".
This isn't rocket science people! This is basic comprehension!
I go back to my All-You-Can-Eat Buffet idea. Has anyone here every had a similar discussion with a restaurant? How did that go?