I've always wondered...absent a manual audit, how would anyone ever know?
IIRC, my Roth account is just one big melting pot...contributions & conversions...no separate lots like I have in my taxable accounts.
I actually thought the same. But if you check your taxes that year, there is a 1099 form that your 401k account holder sent to you for the roll over, it lists the contributions and the earnings separately, thst is how they know… [emoji3]