From the Privacy Rights Clearinghouse:
Initial workers' compensation claims are not public records, but when
a claim is appealed to the Workers’ Compensation Appeals Board (WCAB),
it becomes a public record. Employers may access WCAB records only if
a work-related injury might interfere with your ability to perform a
certain job.
Under the California Labor Code workers’ compensation claims records
may not contain individually identifiable information—which would
include any medical information that is identifiably linked to
you—when accessed by someone who is not a party to the claim. (Cal.
Labor Code § 138.7(a)) An exception to the law allows someone who is
not party to a claim, but who identifies himself and the reason for
the request, to access an identifiable record.
In California, employers can access these records only after a job
offer has been made. They cannot rescind the offer based on
information in the record. (Cal. Labor Code §132(a)) However, if a
workers’ compensation record includes prior claims that you failed to
disclose during the job application process, that can be grounds for
denying employment or for termination if you have already been hired.
To access worker compensation records an employer submits a “Request
for Public Records” to the California Workers’ Compensation Appeals
Board, giving a legitimate reason for the request. If the purpose of
the request is screening prior to employment, but after an offer of
employment has been extended, the Director of the Department of
Workers' Compensation must give you this notice, in 12-point type: “IT
MAY BE A VIOLATION OF FEDERAL AND STATE LAW TO DISCRIMINATE AGAINST A
JOB APPLICANT BECAUSE THE APPLICANT HAS FILED A CLAIM FOR WORKERS'
COMPENSATION BENEFITS.” (Cal. Labor Code § 138.7(b)(5)) As a job
applicant, you’d get this notice, but if you’re not hired, it would be
up to you to prove the reason was that you had previously filed a
workers' compensation claim.
Based on this information, opening or closing a claim prior to application would likely not affect the outcome.