The statement doesn't explicitly state policies in tier 1 or beyond, but state the following;

Employees are trained on an ongoing basis on topics relating to ethics and compliance. We will continue to identify ways to improve employee and supplier awareness of our efforts to eliminate modern slavery from our business and supply chain. We will continue to identify best practices and information that can be applied to our business and supply chain. Airbnb maintains a hotline that allows employees to report concerns, including concerns related to the presence of modern slavery. Airbnb has a Whistleblower Policy that prohibits retaliation against anyone who raises a concern. Reports are investigated according to Airbnb policy and procedure.

Is the following statement (in the "OUR POLICIES ON MODERN SLAVERY" part) regarding the company's standards applied to its suppliers not enough for this question?

"Airbnb will not tolerate modern slavery in our supply chain or in any part of our business. We are committed to ensuring that there is transparency in our own business and to tackling any modern slavery in our supply chain. We expect the same standards from our vendors and contractors. Our Code of Ethics and employment handbook reflect our commitment to ethical business practice and corporate citizenship. We ensure consistent messaging of these policies is distributed throughout our business and management at all levels, as well as in our supply chain. (...) In 2021, we updated our Master Services Agreement to explicitly identify the U.K. Modern Slavery Act as a law our suppliers may have to comply with."

Since, the word 'may be' is used, 'suppliers comply with the laws' is not considered.

Since, modern slavery involves forced labor and it is said that modern slavery will not be tolerated. Therefore, it is considered that forced labor is not tolerated.

Pg. 1

“For the purposes of this statement, the term ‘modern slavery’ encapsulates slavery, servitude, forced or compulsory labour, and human trafficking.”