The easiest way to ask the question is as a simple case study:
Jane has made $100,000 of contributions into her 401k. Her contributions have earned $50,000, so her total balance at retirement is $150,000. She retires from her job and immediately rolls her 401k into a traditional IRA. Assume she converts all $150,000 to a Roth IRA so she can access it in 5 years (Note: aware that nobody would do this given that you only need to convert the amount you intend to spend per year, 5 years from now).
In 5 years, is she only able to access the $100,000 in contributions she had originally made, or can she access the full $150,000. Let's ignore taxes paid or the sake of simplicity?
I am yet to see a definitive answer, though most seem to indicate you can access the full $150,000. That makes sense, given that you already paid taxes on all of it.
Is there a definitive source that verifies this in plain English?