Do 401k plans allow people to buy single stocks? I never saw it in my experience. I cannot believe that would be considered "prudent" by financial regulators. However, when you leave a company you can "roll-over" your 401k into an IRA, then you can go wild and buy anything that you want (IBRK allows it).
i401k’s which you have to manage yourself if you are a contractor allow you to purchase whatever you want depending on where your account is. I was with Vanguard and they do not allow it - I moved my account to etrade and now my 401k account is basically like my brokerage account, I can buy whatever I want.