According to signalling theory, managers are interested in disclose some good news about their performance which are not exist if annual reports, like social activities as well as environmental initiatives.
But about your question related to annual reports plus sustainability reports or just integrated reporting, I am not sure. Actually, I believe the first choice is better and integrated reporting is out of date!
Olga Cucaro the Integrated Report is not a compliance report like the Annual Report and Sustainability Report. The Integrated Report is a stakeholder communication report in which value creation must be communicated towards the stakeholders, therefore supporting the stakeholder theory.
i think Integrated report definitely a communicating report to the stakeholders, which consist of all financial and non-financial information, the quality of the report depends on Materiality and size of the Report