It probably is, the whole reason supersonic passenger flight looked feasible for a bit was that turbine technology hadn’t caught up so slower jets weren’t that much less efficient than supersonic jets.
But fuel concerns aside, it’s kinda silly to compare a billion dollar fighter jet built with 60s technology to a 747-sized aircraft built for passenger flight with modern technology. Just wildly different environments, purposes, and resources.
The rendering in interestingengineering article is a stock image. An older SCMP article gives a much weirder rendering which matches the whitepaper the lead researcher published on I-shaped hypersonic configurations.
So I have no idea what the blurry ass rocket pic is supposed to be, maybe it was a test vehicle for just the engine, maybe SCMP misattributed it, maybe the team dumped the whole “I-shaped configuration” thing.
Presumably any ram or scram-jet engine will require a rocket engine or other assist, assuming it’s not a hybrid like the SR-71.