No, you're doing it because you can withdraw contributions from a Roth IRA with no penalty. The Roth IRA merely exists as a vehicle to get money out of a 401k with no penalty.
In this situation, there is no difference from if you were actually retirement age and withdrawing from your 401k. Same taxes, no penalty.
Hey just wanted to say thanks for explaining that. I had a talk with my RIA and he never suggested it because my position for the past decade of working with him has consistently been that I would be working past IRA penalty age so it wasn't an issue. But we are considering it for other reasons now that I know it exists (e.g., early retirement).
In this situation, there is no difference from if you were actually retirement age and withdrawing from your 401k. Same taxes, no penalty.