Satellites are mostly tied to their orbit in terms of flight path and times. An aircraft can be anywhere at any time, and this one is designed to be anywhere quickly.

It also says it's intended to be unmanned. Which means that what it brings to the table is similar to what a drone brings to the table, just at a much larger scale, it's a global asset drone vs a theater asset drone. Put a couple of em on an airbase in the middle east somewhere and it's only a few hours round trip to go check on what the latest is on ICBM progress in NK, for example. Even less to have a peek at the goings on in Gaza, or Yemen...

We're still flying U2 spy planes, we run drones all over the place, there's absolutely still purposes for this type of platform.

It's also noteworthy that the article mentions mach 10, which is getting ballpark close to being entirely untouchable by air defenses. Top speed for SAMs is ballpark mach 15, but there aren't a whole hell of a lot of missiles that could chase down a target doing mach 10, and if it's stealth tech, even the very best systems would be very hard pressed to acquire it with enough lead time to come up with a fire solution for it. A stealth mach 10 capable platform could fly anywhere on earth with very little regard for potential defenses.

The truly relevant question is actually one you didn't ask. How much is it, and is it worth it? I'd say probably not, but not in the context that we wouldn't be getting our money's worth, I think we would, but I don't think we really need to spend that much to have even more military advantage than we already have.