Health Savings Account - 415 Compensation

[ErisaGooroo]

From the W-2 instructions, I learned that an employer's contribution (including an employee's contributions through a cafeteria plan) to an employee's HSA is not subject to federal income tax withholding or social security, Medicare, or railroad retirement taxes (or FUTA tax). 

I understand that 415 compensation is grossed up to account for elective deferral amounts contributed to a cafeteria 125 plan but what about if the employer contributes to the HSA on behalf of the employee.  Is 415 comp grossed up for the employer contribution to the HSA? And ,if the answer is no, then I assume the plan document would not have to be amended to exclude the HSA employer contribution from the definition of Plan Comp for allocation purposes (SH & ER) because it is not comp for plan purposes.

Total Comp is defined as W-2 Comp and Plan Comp does not currently exclude deferrals / cafeteria. 

Greatly appreciate your input.

QNPG