I'd say it's pretty impressive. Building and igniting a rocket engine is hard. For more detail, I can recommend watching "Why starting a rocket engine is so hard" by Tim Dodd [0].
It's not "never been done before" impressive, they're a few years behind e.g. SpaceX's Raptor engine, which uses the same propellants, and is also reusable. But still, a new rocket engine is no small feat - the engine is probably the hardest part of a rocket. This is quite literally rocket science.