You're right you can shoot slower or even single shot ... but thats why it isn't a *GAME CHANGER*. A Game Changer is something which blows everything else away ... you have pretty much agreed with
@snerkler that 20fps is more than you need; so all it is is headline boasting. Yes it has a purpose, but its not a game changer. Apart from the silent shutter; I'm failing to see much in the admittedly impressive spec's which will actually change significantly the photos which come from (its target market) of sports photographers who are using Nikon D5 or Canon 1DX II. It might be a game changer in terms of mirrorless cameras ... but thats not what people are claiming ... they are claiming its a game changer for CAMERAS.
(PS. no one was saying about the frame rate of the original 1D as it was slower - iirc - than the film cameras of the day)
I would suggest there is also a difference between MP and file sizes which can be handled by increasing the computer's power ... and being able to sort through many more photos is a factor of human endurance / human ability.