U.S. Treasury Direct made it easier to add and change bank accounts as a funding source for your account. Previously they required a paper form with bank notary in order to change your bank. Now, you can easily change banks or even save multiple banks to the same login.
A lot of us hold I Bonds in a Treasury Direct account, and some people buy Treasury Bills there too (though most prefer doing T-Bills through a brokerage).
The change took place a few months back, but it still comes up in discussion periodically and we’ve never spelled this out, so I thought it worth a mention. I’ve even used Treasury Direct as a way of meeting a direct deposit requirement for a bank bonus.