All wireless "unlimited data" plans come with an expiration date. Once a cellular company's sales targets for new customer has been met, they change the "unlimited data" plan.
In this example, it is Sprint which has announced that once you use your monthly "unlimited" allotment of 23 Gig of data, you get throttled.
Exhibit Number One in the Museum of Why Wireless Won't Replace Fiber is data caps. If wireless was so wonderful, the cellular companies would not have to put data caps on their service. But the data caps PROVE that the wireless infrastructure can't handle the demand. If it could, they would not be doing this bait and switch.