This problem is not addressed by any checklist or guideline. The number of authors on a systematic review may change between registration and publication. But clarity as to what roles each author had in the systematic review process is required so that the public can understand who is conducting the research they are reading.
Articles that support this problem:
Increasing number of authors in Cochrane reviews
2020 : Journal of evidence‐based medicine
More than one-third of Cochrane reviews had gift authors, whereas ghost authorship was rare
2020 : Journal of clinical epidemiology
Group authorships in Cochrane had low compliance with Cochrane recommendations
2020 : Journal of evidence-based medicine
Prevalence of honorary and ghost authorship in Cochrane reviews
2002 : Jama