Roth 401k non qualified distribution penalty

[WCC]

This topic was discussed briefly on another thread with a conclusion that concerned me.

Is a non qualified Roth 401(k) cash distribution subject to the 10% early withdrawal penalty? Not just the earnings, but the entire distribution?

I have always thought it was and would be shocked if both the basis and the earnings are not subject to 10%. However, the below paragraph from the IRS site is confusing me. I have also read material that suggests the basis of a non qualified Roth 401(k) distribution is not subject to the early withdrawal penalty.

"Topic 558 - Additional Tax on Early Distributions from Retirement Plans, Other Than IRAs

To discourage the use of retirement funds for purposes other than normal retirement, the law imposes a 10% additional tax on certain early distributions from certain retirement plans. The additional tax is equal to 10% of the portion of the distribution that is includible in income. .....

Any clarification would be great as I cannot find a direct statement that says the Roth 401k basis is not subject to the 10% penalty in a non qualified distribution.