Which systems the statement concerned
On July 19, 2021, the UK government joined partners in attributing attacks exploiting Microsoft Exchange servers to Chinese state-backed actors. Exchange servers provide organizational email and related functions. The statement concerned access to affected networks, rather than a finding that every Windows computer, Outlook account or Microsoft cloud service had been compromised.
Source [1]What an attribution statement can establish
A government's attribution identifies whom it assesses to be responsible. It is not the same document as a criminal charge, court verdict or technical account of every victim. Precise reporting should name the government making the assessment and the systems involved.
For organizations, a historical incident report is background, not a substitute for current security advisories and supported patches. The linked Twitch explainer shows a similar need for scope: a confirmed leak of certain information does not justify saying all user data or every credential was exposed. This page preserves the dated attribution without expanding it into unsupported claims about unrelated services.
Source [1]