It can be seen that whoever signs a contract with PB clause has the responsibility to open PB. In other words, the contractor who has not signed the terms of the performance bond is not responsible for issuing the performance bond.
For this case, if the contract signed by the Hong Kong company as an intermediary with foreign buyers contains PB clauses, but the contract signed with the actual mainland suppliers does not contain PB clauses, then the Hong Kong company will open PB for foreign buyers, and the mainland suppliers do not need to open PB.
If the contracts signed by Hong Kong middlemen and mainland suppliers also contain PB clauses, then mainland suppliers also need to open PB for Hong Kong middlemen.