OP, at first it would have been nice if you had explained better what you meant by "retirement account" in context, as not everybody gets it clear here what you meant by the word retirement account, as the majority of the people here are from nations or regions where such is not conversant with them, and besides this is a global platform so people would be curious to know what it means from your explanations even if I am aware of it, others too will need to have a little brief on what you meant by that.
Read
https://www.investopedia.com/terms/1/401kplan.aspIt's like you work under someone, then your boss didn't give all amount of your monthly salary, but some part are automatically invested. But, you're the one who choose which assets that you want to invest.
Do not forget that they also want tax, and do not forget that they will always want to get them KYCed as well.
For sure the government will know everything of your cryptocurrencies.
I treat people who invest in Bitcoin through 401k is similar to buy Bitcoin ETFs, both need to trust the company who custody it and the government.