The commercial invoice must be issued by the beneficiary specified in the letter of credit, right?

Yes, it must be issued by the beneficiary specified in the letter of credit. The requirements of UCP600 for commercial invoices:

A. unless otherwise stipulated in the credit, commercial invoice:

1) must be in favor of the beneficiary specified in the letter of credit.

2) The applicant of the letter of credit must be the beneficiary.

3) No signature is required

Unless otherwise stipulated in the letter of credit, banks may refuse to accept commercial invoices with an amount exceeding the amount allowed in the letter of credit.

The description of the goods in the commercial invoice must be consistent with that in the letter of credit. In all other documents, the description of the goods can use common terms that do not contradict the description of the goods in the letter of credit.