Without the benefit of the employer portion of the SSI tax, everyone would be paying double what they do now. It’s certainly a cost to the employer and a benefit to the employee. You may not want to call it compensation, but it certainly is when contextualized properly, or at least will be compensatory at some point in the future. Work comp insurance is definitely overhead, but can also become compensatory as well. The employee sure doesn’t pay for it - besides in lower wages because of it anyhow, so I would argue that one either way.
Payroll taxes are just that: taxes. They are reported that way on your W-2 form.
If your employer pays the premium on a life insurance policy and you or your next of kin (not the employer) is listed as the beneficiary, then the premium is reported as taxable income on your W-2 form.
The key here is that real compensation only counts if the benefit accrues now, not at some unspecified point in the future when SSI may not even be solvent.