Legally, Red Bull Racing Ltd., the Formula 1 team, didn't reach any milestone and aren't launching their first engine.
Red Bull Powertrain 2026 Ltd. is the company launching a new engine.
Red Bull incorporated a new company, Red Bull Powertrain 2026 Ltd., back in late-May. While still under the Red Bull GmbH corporate umbrella, it is it's own distinct company, separate from Red Bull Racing Ltd. and Red Bull Powertrain Ltd., which is the company responsible for the current Honda-handoff engine.
This was done to maximize benefits given to "new" engine manufacturers, as full benefits for a new engine launched by an existing constructor, Red Bull Racing Ltd. and Red Bull Powertrain Ltd., may be in doubt.