RRはすでにDX設計でいくつかの民航機用エンジンを実際に開発して証明した上で今回軍用にそれを転用し、
さらにその実証も兼ねてオルフェウスを作っているからDXでも日本より経験があるでしょ

Rolls-Royce has already proved it can develop new versions of commercial engines
in five years and is confident the same can be achieved in the military engine domain, too.
“We can’t repeat what we did on the Typhoon with 20-year lead times and costs; we’ve got to
really compress this,” Zino says.
Such design and engineering approaches are critical to development of the Tempest platform, airframe and sensors.
Achieving such an accelerated development would allow the Tempest combat aircraft to
achieve an initial operational capability around 2035.
Rolls-Royce and IHI will work on the demonstrator until around 2026, when key decisions about
moving into a full development program will be made. (22/02/02 Aviation Weeks)

あとDXとは関係ないがこれ見ても共同実証エンジンは当初26年頃までやる予定だったのでGCAPの実証エンジンも
その辺で一区切りありそうだな