It's not a consequence of this.

And that's their... third... fourth? completely separate system for connecting an AWS virtual network to a physical DC in the outside world?

Yes, there are several other options. This is the first one that is not metered.

	▲	everfrustrated 3 days ago \| parent [-]
		Might not be GB metered, but it is metered by the port-size/Hour at a very heavily marked up rate.