Anything that describes competencies instead of duties, omits the named profession, states a period that does not match the work, or conflicts with the credential being supplied.
Read the draft as a stranger would
Employer letters are usually assembled from internal job postings, which are written to attract candidates rather than to answer an officer's questions. The result lists attributes and leaves the actual work vague. The applicant should read the draft as someone unfamiliar with the industry and mark every sentence that raises a question instead of answering one.
Then ask for specific changes: name the profession, describe the duties concretely, state the period sought and why, set out the terms, and have it signed by someone with authority to bind the employer. Where the letter would have to overstate the role to look convincing, that is a signal about the role rather than about the letter, and it should be treated as one. It is a reasonable request to make and most employers accommodate it readily once the reason is explained.