Except this is no longer true in a full-duplex world, you can approach 99% utilization on Ethernet at full-duplex. At the time token-ring was competitive, full-duplex Ethernet was just emerging. While IBM's marketing and some of the complexity of token-ring hurt it, what really killed it was the widespread emergence of full-duplex ethernet switches which basically eliminated the under-utilization problem while not having the complexity of dealing with a token-ring network.

Except they are not "throttling" you, they are just giving you lower priority IF you use over 80% of your bandwidth for 15 minutes AND the whole segment is over 70% utilization. This means that grandma can still get her mail when you are seeding the new release of Ubuntu, but you "lose" bandwidth if you actually hit 100% congestion.