3GPP 21.900 v20.0.0 — the document's own text
6.7 Guidance for Appointed Duties
Taught in 2. The shape of 3GPP, and what the record does not say about it (How standards actually get made, in depth).
As part of progressing a work item or other business of 3GPP, delegates may be appointed to roles such as rapporteur, moderator, editor, etc. While operating in these roles, delegates are expected to carry out their assigned duties with impartiality and in the interests of 3GPP. While company support letters are not required to assume these roles, it is expected that any delegate taking on these responsibilities has the support of their company in fulfilling the associated duties.
3GPP delegates appointed to roles such as rapporteur, moderator, editor, etc., shall attend a 3GPP Compliance Training session (refer Article 12 of 3GPP Working Procedures [8]) as soon as possible after their appointment, and at least once every two years during their mandate.