This is because those funds will already have been tested for lifetime allowance purposes through BCE 1 and, if it applied, BCE 5A or 5B. (gov.uk)
«Under the new lifetime allowance of # 1m, set to be introduced in April 2016, the maximum pension someone is able to receive without the pension fund incurring a tax charge will be around # 34,000 annually, reduced from # 42,000 (assuming they choose not to receive a tax - free cash sum from their pension plan) ¹. (lawyer-monthly.com)
You don't have to enrol an employee if they give you proof of their lifetime allowance protection. (gov.uk)