You are not being taxed twice.
You are taxed once on your 2020 tax return. 1099-R box 4 withholding is just estimating the tax and goes on line 25c on your 1040 form and offsets your overall tax liability - just like W-2 withholding.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
