Comment by SkyMarshal
18 hours ago
I think part of it was that they were testing a new aerodynamic design that eliminates or minimizes sonic boom, so they can go supersonic over land almost immediately after takeoff, and operate over populated land routes. It makes sense to test that kind of thing with the smallest possible model first, then see if you can scale it up to passenger size without losing that quiet acceleration. Their timeline for doing that may be optimistic, but what they're doing makes sense.
The XB-1 doesn't have any boom reduction shaping. That's the NASA X-59, though that aircraft is pretty much a dead-end in that it's not scalable to a passenger configuration.
The XB-1 made use of an atmospheric trick to minimise boom propagation to ground level on one test flight, so well-known in fact that Concorde sometimes used it to accelerate as it coasted-out without an audible ground-level boom. Unfortunately that trick runs out at about M1.17.