The same SHRM article answers this question: https://www.shrm.org/hr-today/news/hr-magazine/pages/0113-wrap-documents.aspx
While large employers may have the resources to prepare custom plan documents and summary plan descriptions for each employee welfare benefit plan they sponsor, most small employers lack the time, money and expertise to prepare these documents and keep them up-to-date in an ever-changing regulatory landscape. One simple and cost-effective solution is the wrap document.
A wrap document is a relatively simple document that “wraps” around the insurance policy, coverage certificate or plan booklet. The benefits available under the plan continue to be governed by the insurance policy, coverage certificate or plan booklet, while the wrap document supplements with the information necessary to comply with ERISA. In effect, the wrap document fills the gaps left by insurance carriers and third-party administrators.
The same SHRM article answers this question: https://www.shrm.org/hr-today/news/hr-magazine/pages/0113-wrap-documents.aspx
