What it covers. A NIST draft publication describing how to measure the integrity of BIOS and system firmware and report those measurements so that unauthorised changes can be detected. It was published as a draft and was not finalised, though its concepts are reflected in later firmware resiliency guidance such as SP 800-193.
In practice. Organisations use hardware roots of trust, measured boot and attestation to check that firmware matches known good values, and include firmware in monitoring. Procurement favours platforms that support these features. Evidence includes configuration of measured boot, attestation reports and firmware baselines.
Common gaps. Common gaps are no visibility of firmware state and capabilities available in hardware but never enabled. Its draft status also means it is best read as background rather than a requirement.