Employer Insurance Savings Schemes (salary sacrifice)- EISS

Suba

My husband's employer has offered an EISS to the staff which would involve a salary sacrifice which would then become a non- cash benefit of a death benefit of 2 times salary. In addition we accrue a premium fund which we can take out after 5 years untaxed. So that we don't lose out the provider loans an amount (without interest) equal to that which we lost (salary sacrifice - NI and tax) bringing his wages up to it's original amount, repaying the loan when we take the money from the premium fund thus effectively giving us the tax and NI that we didn't pay but in five years time?
How can this be right and why is the money from the premium fund not taxable?
Other than the usual salary sacrifice pitfalls is there anything else I should worry about?
The provider is Corporate Solutions.