这个是不可能的：“结婚后401K忘了改名字，结果配偶拿不到”

根据你给的连接：

”What’s more, if you’re married a federal law says a surviving spouse is automatically the beneficiary of 401(k) funds. To leave the money to someone other than your spouse, that person must be named on a beneficiary form, and your spouse must sign a waiver relinquishing any right to the money.“