Yikes, that seems pretty horrendous law. In the the UK the tax exempt status comes from the fact you're locking away the income for, say, decades; and you'll be liable to normal income tax at the point of withdrawal.
It's designed to encourage people to save money into their pensions, to make up for decades of the government underfunding social security pensions. It seems really shitty to make that tax break conditional on job security.
